Electrode protection in both aqueous and non-aqueous electromechanical cells, including rechargeable lithium batteries

ABSTRACT

Electrode protection in electrochemical cells, and more specifically, electrode protection in both aqueous and non-aqueous electrochemical cells, including rechargeable lithium batteries, are presented. In one embodiment, an electrochemical cell includes an anode comprising lithium and a multi-layered structure positioned between the anode and an electrolyte of the cell. A multi-layered structure can include at least a first single-ion conductive material layer (e.g., a lithiated metal layer), and at least a first polymeric layer positioned between the anode and the single-ion conductive material. The invention also can provide an electrode stabilization layer positioned within the electrode, i.e., between one portion and another portion of an electrode, to control depletion and re-plating of electrode material upon charge and discharge of a battery. Advantageously, electrochemical cells comprising combinations of structures described herein are not only compatible with environments that are typically unsuitable for lithium, but the cells may be also capable of displaying long cycle life, high lithium cycling efficiency, and high energy density.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/500,097, entitled “Electrode Protection in both Aqueous andNon-Aqueous Electrochemical Cells, Including Rechargeable LithiumBatteries,” filed Jul. 9, 2009 which is a divisional application of U.S.patent application Ser. No. 11/400,025, entitled “Electrode Protectionin both Aqueous and Non-Aqueous Electrochemical Cells, IncludingRechargeable Lithium Batteries”, filed Apr. 6, 2006 which claimspriority under 35 U.S.C. §119(e) to U.S. Provisional Application Ser.No. 60/785,768, entitled, “Lithium/Water, Lithium/Air Batteries,” filedon Mar. 22, 2006, each of which is incorporated herein by reference inits entirety.

FIELD OF INVENTION

The present invention relates to electrode protection in electrochemicalcells, and more specifically, to electrode protection in both aqueousand non-aqueous electrochemical cells including rechargeable lithiumbatteries.

BACKGROUND

There has been considerable interest in recent years in developing highenergy density batteries with lithium containing anodes. Lithium metalis particularly attractive as the anode of electrochemical cells becauseof its extremely light weight and high energy density, compared forexample to anodes, such as lithium intercalated carbon anodes, where thepresence of non-electroactive materials increases weight and volume ofthe anode, and thereby reduces the energy density of the cells, and toother electrochemical systems with, for example, nickel or cadmiumelectrodes. Lithium metal anodes, or those comprising mainly lithiummetal, provide an opportunity to construct cells which are lighter inweight, and which have a higher energy density than cells such aslithium-ion, nickel metal hydride or nickel-cadmium cells. Thesefeatures are highly desirable for batteries for portable electronicdevices such as cellular phones and laptop computers where a premium ispaid for low weight. Unfortunately, the reactivity of lithium and theassociated cycle life, dendrite formation, electrolyte compatibility,fabrication and safety problems have hindered the commercialization oflithium cells.

Lithium battery systems generally include a cathode which iselectrochemically lithiated during the discharge. In this process,lithium metal is converted to lithium ion and transported throughelectrolyte to the battery's cathode where it is reduced. In alithium/sulfur battery, lithium ion forms one of a variety of lithiumsulfur compounds, at the cathode. Upon charging, the process isreversed, and lithium metal is plated, from lithium ion in theelectrolyte, at the anode. In each discharge cycle, a significant number(e.g., 15-30%) of available Li may be electrochemically dissolved in theelectrolyte, and nearly this amount can be re-plated at the anode uponcharge. Typically, slightly less lithium is re-plated at the anode ateach charge, as compared to the amount removed during each discharge; asmall fraction of the metallic Li anode typically is lost to insolubleelectrochemically inactive species during each charge-discharge cycle.

This process is stressful to the anode in many ways, and can lead topremature depletion of Li and reduction of the battery cycle life.During this cycling, the Li anode surface can become roughened (whichcan increase the rate of field-driven corrosion) and Li surfaceroughening can increase proportionally to the current density. Many ofthe inactive reaction products associated with overall Li loss from theanode upon cycling can also accumulate on the increasingly roughened Lisurface and may interfere with charge transport to the underlyingmetallic Li anode. In the absence of other degradation processes inother parts of the battery, the per-cycle Li anode loss alone caneventually render the cell inactive. Accordingly, it is desirable tominimize or inhibit Li-loss reactions, minimize the Li surfaceroughness/corrosion rate, and prevent any inactive corrosion reactionproducts from interfering with charge transport across the Li anodesurface. Especially at higher current density (which is commerciallydesirable) these processes can lead to quicker cell death.

The separation of a lithium anode from the electrolyte of a rechargeablelithium battery or other electrochemical cell can be desirable for avariety of reasons, including the prevention of dendrite formationduring recharging, reaction of lithium with the electrolyte, and cyclelife. For example, reaction of a lithium anode with the electrolyte mayresult in the formation of resistive film barriers on the anode, whichcan increase the internal resistance of the battery and lower the amountof current capable of being supplied by the battery at the ratedvoltage. Many different solutions have been proposed for the protectionof lithium anodes in such devices, including coating the lithium anodewith interfacial or protective layers formed from polymers, ceramics, orglasses, the important characteristic of such interfacial or protectivelayers being to conduct lithium ions. For example, U.S. Pat. Nos.5,460,905 and 5,462,566 to Skotheim describe a film of an n-dopedconjugated polymer interposed between the alkali metal anode and theelectrolyte. U.S. Pat. No. 5,648,187 to Skotheim and U.S. Pat. No.5,961,672 to Skotheim et al. describe an electrically conductingcrosslinked polymer film interposed between the lithium anode and theelectrolyte, and methods of making the same, where the crosslinkedpolymer film is capable of transmitting lithium ions. U.S. Pat. No.5,314,765 to Bates describes a thin layer of a lithium ion conductingceramic coating between the anode and the electrolyte. Yet furtherexamples of interfacial films for lithium containing anodes aredescribed, for example, in U.S. Pat. Nos. 5,387,497 and 5,487,959 toKoksbang; U.S. Pat. No. 4,917,975 to De Jonghe et al.; U.S. Pat. No.5,434,021 to Fauteux et al.; and U.S. Pat. No. 5,824,434 to Kawakami etal.

A single protective layer of an alkali ion conducting glassy oramorphous material for alkali metal anodes, for example, lithium anodesin lithium-sulfur cells, is described in U.S. Pat. No. 6,02,094 to Viscoet al. to address the problem of short cycle life.

While a variety of techniques and components for protection of lithiumand other alkali metal anodes are known, especially in rechargeablebatteries, these protective coatings present particular challenges.Since lithium batteries function by removal and re-plating of lithiumfrom a lithium anode in each charge/discharge cycle, lithium ion must beable to pass through any protective coating. The coating must also beable to withstand morphological changes as material is removed andre-plated at the anode.

Rechargeable (secondary) lithium batteries present a particularchallenge in connection with their use with aqueous electrolytes. Water,and hydrogen ions, are particularly reactive with lithium. Such devices,to be successful in achieving long cycle life, will require very goodprotection of the lithium anode.

Despite the various approaches proposed for forming lithium anodes andforming interfacial and/or protective layers, improvements are needed,especially for lithium anodes designed for use in aqueous and/or airenvironments.

SUMMARY OF THE INVENTION

Electrode protection in electrochemical cells, and more specifically,electrode protection in both aqueous and non-aqueous electrochemicalcells, including rechargeable lithium batteries, are presented.

In one aspect, an electrochemical cells is provided. The electrochemicalcell comprises an electrode comprising a base electrode materialcomprising an active electrode species that is depleted and replatedupon discharge and charge, respectively, of the electrode. The electrodecomprises a first layer comprising the active electrode species, asecond layer comprising the active electrode species, and a single-ionconductive layer separating the first layer from the second layer andsubstantially preventing electronic communication between the first andsecond layers across the layer. The second layer is positioned so as toreside between the first layer and an electrolyte used with the cell.

In another aspect, a method of electrical energy storage and use isprovided. The method comprises providing an electrochemical cellcomprising an electrode comprising a base electrode material comprisingan active electrode species that is depleted and replated upon dischargeand charge, respectively, of the electrode, wherein the electrodecomprises a first layer comprising the active electrode species, asecond layer comprising the active electrode species, a single-ionconductive layer separating the first layer from the second layer andsubstantially preventing electronic communication between the first andsecond layers across the single-ion conductive layer, wherein the secondlayer is positioned between the first layer and an electrolyte used withthe cell. The method also comprises alternately discharging current fromthe device to define an at least partially discharged device, and atleast partially charging said at least partially discharged device todefine an at least partially recharged device, whereupon the baseelectrode material from the first layer is consumed upon discharge to agreater extent than it is replated upon charge, and base electrodematerial is replenished into the first layer, from the second layer,across the single-ion conductive, non-electronically conductive layer.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying figures. In cases where the present specification and adocument incorporated by reference include conflicting and/orinconsistent disclosure, the present specification shall control. If twoor more documents incorporated by reference include conflicting and/orinconsistent disclosure with respect to each other, then the documenthaving the later effective date shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale. In the figures,each identical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled in every figure, nor is every component of eachembodiment of the invention shown where illustration is not necessary toallow those of ordinary skill in the art to understand the invention. Inthe figures:

FIG. 1 shows a structure for use in an electrochemical cell, including asingle-ion conductive layer and a polymer layer, according to oneembodiment of the invention;

FIG. 2 shows a structure for use in an electrochemical cell, includingseveral multi-layered structures, according to an embodiment of theinvention;

FIG. 3 shows a structure for use in an electrochemical cell, includingan embedded layer, according to an embodiment of the invention;

FIG. 4 shows a structure for use in an electrochemical cell, includingan embedded layer comprising a multi-layered structure, according to anembodiment of the invention;

FIG. 5 shows SEM images of Li anode surfaces after a 10^(th) discharge,according to an embodiment of the invention;

FIG. 6 shows a schematic diagram of an embodiment that increases thebarrier to passage of a species;

FIG. 7 shows a structure for use in an electrochemical cell, includingseveral multi-layered structures, embedded layers, and separationlayers, according to an embodiment of the invention; and

FIG. 8 shows SEM images of Li anode surfaces after a 1^(st) discharge,according to an embodiment of the invention.

DETAILED DESCRIPTION

The present invention relates to electrode protection in electrochemicalcells, and more specifically, to electrode protection in both aqueousand non-aqueous electrochemical cells, including rechargeable lithiumbatteries. In most embodiments described herein, lithium rechargeablebatteries (including lithium anodes) are described. However, whereverlithium batteries are described herein, it is to be understood that anyanalogous alkali metal battery (alkali metal anode) can be used.Additionally, although rechargeable batteries are primarily disclosedherein, non-rechargeable (primary) batteries are intended to benefitfrom the invention as well. Furthermore, although the invention isparticularly useful in providing anode protection, such that high-cyclelife aqueous rechargeable batteries (batteries using an aqueous-basedelectrolyte) are enabled, the invention is also applicable tonon-aqueous-based electrolyte batteries.

The invention provides techniques and components for superior protectionof and/or maintenance of electrodes (especially lithium anodes) inrechargeable and other batteries. Components of the invention provide,at least, one or more of the following features: (1) protection of anelectrode from one or more components of an electrolyte that can reactwith or otherwise hasten the demise of (shorten the cycle life of) theelectrode and/or overall device, (2) control over dissolution of anodematerial into electrolyte (e.g., reduction of lithium to lithium ion),and re-plating of electrode material from the electrolyte (e.g.,oxidation of lithium ion to lithium metal), at the anode, and/or (3)superior control of desirable passage of components from the electrodeto the electrolyte (e.g., lithium ion) while inhibiting passage ofundesirable components from the electrolyte to the electrode that candamage the electrode.

In one embodiment, an electrochemical cell of the invention includes ananode comprising lithium, and a multi-layered structure positionedbetween the anode and an electrolyte of the cell. In one specificembodiment providing superior interaction between the multi-layeredstructure and the electrode, the multi-layered structure includes atleast a first single-ion conductive material layer (e.g., a lithiatedmetal layer), and at least a first polymeric layer positioned betweenthe anode and the single-ion conductive material. In this embodiment,the multi-layered structure can include several sets of alternatingsingle-ion conductive material layers and polymeric layers. Themulti-layered structures can allow passage of lithium ions, whilelimiting passage of certain chemical species that may adversely affectthe anode (e.g., water). The cells may also include an separation layer(e.g., a plasma-treated layer) positioned between the anode and themulti-layered structure. This separation layer can act as a temporary orpermanent protective layer, e.g., to cause uniform depletion and/orre-plating of lithium across the surface of the anode.

As noted in the embodiment thus far described, a lithium electrode, withor without a separation layer, is first directly addressed by apolymeric layer. On the side of the polymeric layer opposite that of theelectrode, a single-ion conductive material layer is provided.Additional layers can be further provided. This arrangement can providesignificant advantage, as polymers can be selected that impartflexibility to the system where it can be needed most, namely, at thesurface of the electrode where morphological changes occur upon chargeand discharge. In one specific embodiment, the polymer is particularlypliable and/or elastic (non-brittle) to provide a particularly durable,robust, rechargeable battery. In this arrangement the polymer can haveat least one of the following properties, or a combination of any numberof these properties: a Shore A hardness of less than 100, less than 80,less than 60, less than 40, or less than 20, (or a Shore A hardnessbetween 0 and 10, between 10 and 20, between 20 and 30, between 30 and40, between 40 and 50, between 50 and 60, between 60 and 70, between 70and 80, between 80 and 90, or between 90 and 100), or a Shore D hardnessof less than 100, less than 80, less than 60, less than 40, or less than20 (or a Shore D hardness between 0 and 10, between 10 and 20, between20 and 30, between 30 and 40, between 40 and 50, between 50 and 60,between 60 and 70, between 70 and 80, between 80 and 90, or between 90and 100); a Young's Modulus (elastic modulus) of less than 10 GPa, lessthan 5 GPa, less than 3 GPa, less than 1 GPa, less than 0.1 GPa, or lessthan 0.01 GPa (or a Young's Modulus between 0.01 and 0.1 GPa, between0.1 and 1 GPa, between 1 and 2.5 GPa, between 2.5 and 5 GPa); and anaverage fracture toughness of greater than 0.1 MN/m^(3/2), greater than0.5 MN/m^(3/2), greater than 1.0 MN/m^(3/2), greater than 2.0MN/m^(3/2), greater than 3.0 MN/m^(3/2), or greater than 5 MN/m^(3/2)(e.g., as measured at room temperature and atmospheric pressure).Appropriate polymers may also be chosen based on one or more propertiesrelevant to use in an environment as described herein, such as: glasstransition temperature (T_(g)), melting point (T_(m)), strength (e.g.,compressional, tensile, flexural, and yield strength), elongation,plasticity, and hardness (e.g., as measured by a Shore A or Shore Ddurometer, or the Rockwell hardness test). This arrangement, comprisinga depletable/re-platable electrode, polymer protective layer, andsingle-ion-conductive layer as a sub-combination of an overallprotective structure or overall battery, adds significant advantage. Inthis and other arrangements, single-ion-conductive layers can beselected among those described herein and generally known in the artincluding glasses, lithiated metal layers, and the like.

Most single thin film materials, when deposited on the surface of a Lianode, do not have all of the necessary properties of passing Li ions,forcing a substantial amount of the Li surface to participate in currentconduction, protecting the metallic Li anode against certain species(e.g., liquid electrolyte and/or polysulfides generated from asulfur-based cathode) migrating from the cathode, and impeding highcurrent density-induced surface damage. The present inventors havedeveloped solutions to these problems through several embodiments of theinvention, including the use of multi-layered anode stabilization layers(electrode stabilization), embedded Li layers (e.g., embodimentsincluding a first Li layer, a Li conducting and electron insulatinglayer, and a second Li layer), and separation layers (e.g., plasmatreated layers), as discussed in greater detail below.

FIG. 1 shows one example of an electrode protective arrangement of theinvention, exemplified as a multi-layered anode stabilization layerstructure. In the embodiment illustrated in FIG. 1, structure 10includes anode 20 comprising a base electrode material (e.g., lithium),and multi-layered structure 22 covering the anode. In some cases herein,the anode is referred to as an “anode based material,” “anode activematerial,’ or the like, and the anode along with any protectivestructures are referred to collectively as the “anode.” All suchdescriptions are to be understood to form part of the invention. In thisparticular embodiment, multi-layered structure 22 includes single-ionconductive material 50, polymeric layer 40 positioned between the baseelectrode material and the single-ion-conductive material, andseparation layer 30 (e.g., a layer resulting from plasma treatment ofthe electrode) positioned between the electrode and the polymeric layer.Multi-layered structures can allow passage of lithium ions and mayimpede the passage of other components that may otherwise damage theanode. Advantageously, multi-layered structures can reduce the number ofdefects and thereby force a substantial amount of the Li surface toparticipate in current conduction, impede high current density-inducedsurface damage, and/or act as an effective barrier to protect the anodefrom certain species (e.g., electrolyte and/or polysulfides), asdiscussed in greater detail below.

Anode 20 can comprise a base electrode material such as lithium metal,which can serve as the anode active material. The lithium metal may bein the form of, e.g., a lithium metal foil or a thin lithium film thathas been deposited on a substrate, as described below. The lithium metalmay also be in the form of a lithium alloy such as, for example, alithium-tin alloy or a lithium aluminum alloy.

In this and other embodiments, the thickness of the anode may vary from,e.g., about 2 to 200 microns. For instance, the anode may have athickness of less than 200 microns, less than 100 microns, less than 50microns, less than 25 microns, less than 10 microns, or less than 5microns. The choice of the thickness may depend on cell designparameters such as the excess amount of lithium desired, cycle life, andthe thickness of the cathode electrode. In one embodiment, the thicknessof the anode active layer is in the range of about 2 to 100 microns. Inanother embodiment, the thickness of the anode is in the range of about5 to 50 microns. In another embodiment, the thickness of the anode is inthe range of about 5 to 25 microns. In yet another embodiment, thethickness of the anode is in the range of about 10 to 25 microns.

The device illustrated in FIG. 1. may further comprise a substrate, asis known in the art, on the surface of the anode opposite that of themulti-layer structure. Substrates are useful as a support on which todeposit the anode active material, and may provide additional stabilityfor handling of thin lithium film anodes during cell fabrication.Further, in the case of conductive substrates, a substrate may alsofunction as a current collector useful in efficiently collecting theelectrical current generated throughout the anode and in providing anefficient surface for attachment of electrical contacts leading to anexternal circuit. A wide range of substrates are known in the art ofanodes. Suitable substrates include, but are not limited to, thoseselected from the group consisting of metal foils, polymer films,metallized polymer films, electrically conductive polymer films, polymerfilms having an electrically conductive coating, electrically conductivepolymer films having an electrically conductive metal coating, andpolymer films having conductive particles dispersed therein. In oneembodiment, the substrate is a metallized polymer film. In otherembodiments, described more fully below, the substrate may be selectedfrom non-electrically-conductive materials.

The layers of the anode structure 10 of the present invention may bedeposited by any of a variety of methods generally known in the art,such as physical or chemical vapor deposition methods, extrusion, andelectroplating. Examples of suitable physical or chemical vapordeposition methods include, but are not limited to, thermal evaporation(including, but not limited to, resistive, inductive, radiation, andelectron beam heating), sputtering (including, but not limited to,diode, DC magnetron, RF, RF magnetron, pulsed, dual magnetron, AC, MF,and reactive), chemical vapor deposition, plasma enhanced chemical vapordeposition, laser enhanced chemical vapor deposition, ion plating,cathodic arc, jet vapor deposition, and laser ablation.

Deposition of the layers may be carried out in a vacuum or inertatmosphere to minimize side reactions in the deposited layers whichcould introduce impurities into the layers or which may affect thedesired morphology of the layers. In some embodiments, anode activelayers and the layers of multi-layered structures are deposited in acontinuous fashion in a multistage deposition apparatus.

Specifically, methods for depositing anode 20 (e.g., in the case of analkali metal anode such as lithium) onto a substrate include methodssuch as thermal evaporation, sputtering, jet vapor deposition, and laserablation. Alternatively, where the anode comprises a lithium foil, or alithium foil and a substrate, these can be laminated together by alamination process as known in the art, to form an anode layer.

In some embodiments, the single-ion conductive material isnon-polymeric. E.g., in certain embodiments, the single-ion conductivematerial 50 is defined in part or in whole by a metal layer that ishighly conductive toward lithium and minimally conductive towardelectrons. In other words, the single-ion conductive material may be oneselected to allow lithium ions, but to impede electrons, from passingacross the layer. The metal layer may comprise a metal alloy layer,e.g., a lithiated metal layer especially in the case where a lithiumanode is employed. The lithium content of the metal alloy layer may varyfrom about 0.5% by weight to about 20% by weight, depending, forexample, on the specific choice of metal, the desired lithium ionconductivity, and the desired flexibility of the metal alloy layer.Suitable metals for use in the single-ion conductive material include,but are not limited to, Al, Zn, Mg, Ag, Pb, Cd, Bi, Ga, In, Ge, Sb, As,and Sn. Sometimes, a combination of metals, such as the ones listedabove, may be used in a single-ion conductive material.

In other embodiments, the single-ion conductive material may include aceramic layer, for example, a single ion conducting glass conductive tolithium ions. Suitable glasses include, but are not limited to, thosethat may be characterized as containing a “modifier” portion and a“network” portion, as known in the art. The modifier may include a metaloxide of the metal ion conductive in the glass. The network portion mayinclude a metal chalcogenide such as, for example, a metal oxide orsulfide. Single-ion conductive layers may include glassy layerscomprising a glassy material selected from the group consisting oflithium nitrides, lithium silicates, lithium borates, lithiumaluminates, lithium phosphates, lithium phosphorus oxynitrides, lithiumsilicosulfides, lithium germanosulfides, lithium oxides (e.g., Li₂O,LiO, LiO₂, LiRO₂, where R is a rare earth metal), lithium lanthanumoxides, lithium titanium oxides, lithium borosulfides, lithiumaluminosulfides, and lithium phosphosulfides, and combinations thereof.In one embodiment, the single-ion conductive layer comprises a lithiumphosphorus oxynitride in the form of an electrolyte. Electrolyte filmsof lithium phosphorus oxynitride suitable for use as the single ionconductive material 50 are disclosed, for example, in U.S. Pat. No.5,569,520 to Bates. The selection of the single ion conducting materialwill be dependent on a number of factors including, but not limited to,the properties of electrolyte and cathode used in the cell.

For cells used in a water and/or air environment, such as a rechargeablebattery with an aqueous-based electrolyte, the single-ion conductivematerial may be constructed so as to impede the passage of hydrogen ions(protons) across its layer. For instance, during discharge protons maymove against the electric field in a protective layer (e.g., amulti-layered structure) of a cell. However, during charge, the electricfield may accelerate the penetration of protons across the protectivelayer. Eventually protons may reach a Li anode layer and generate, e.g.,hydrogen gas or other species, which may form bubbles and can causedelamination, or other undesirable effects, in a multi-layeredstructure. As discussed in more detail below, the single-ion conductivelayer may be combined with other materials (e.g., impregnated with apolymer) to impede the passage of hydrogen ions and/or or electrons,while permitting the passage of lithium ions.

The thickness of a single-ion conductive material layer (e.g., within amulti-layered structure) may vary over a range from about 1 nm to about10 microns. For instance, the thickness of the single-ion conductivematerial layer may be between 1-10 nm thick, between 10-100 nm thick,between 100-1000 nm thick, between 1-5 microns thick, or between 5-10microns thick. The thickness of a single-ion conductive material layermay be no greater than, e.g., 10 microns thick, no greater than 5microns thick, no greater than 1000 nm thick, no greater than 500 nmthick, no greater than 250 nm thick, no greater than 100 nm thick, nogreater than 50 nm thick, no greater than 25 nm thick, or no greaterthan 10 nm thick. In some cases, the single-ion conductive layer has thesame thickness as a polymer layer in a multi-layered structure.

The single-ion conductive layer may be deposited by any suitable methodsuch as sputtering, electron beam evaporation, vacuum thermalevaporation, laser ablation, chemical vapor deposition (CVD), thermalevaporation, plasma enhanced chemical vacuum deposition (PECVD), laserenhanced chemical vapor deposition, and jet vapor deposition. Thetechnique used may depend on the type of material being deposited, thethickness of the layer, etc.

In some embodiments, single-ion conducting layers can be treated with apolymer such that pinholes and/or nanopores of the single-ion conductinglayers may be filled with the polymer. Such embodiments can impede thediffusion of certain species (e.g., electrolyte and/or polysulfides)towards the anode, e.g., by increasing the distance, and tortuosity,through which such a species would need to pass to penetrate the entiremulti-layer arrangement to arrive at the anode, as discussed in greaterdetail below.

The thickness of a polymer layer (e.g., within a multi-layeredstructure) may vary over a range from about 0.1 microns to about 10microns. For instance, the thickness of the polymer layer may be between0.1-1 microns thick, between 1-5 microns thick, or between 5-10 micronsthick. The thickness of a polymer layer may be no greater than, e.g., 10microns thick, no greater than 5 microns thick, no greater than 2.5microns thick, no greater than 1 micron thick, no greater than 0.5microns thick, or no greater than 0.1 microns thick.

In some embodiments including a multi-layered structure having more thanone polymer layer, the thicknesses of the polymer layers can vary withinthe structure. For instance, in some cases, the polymer layer closest tothe anode layer (e.g., a Li reservoir) is thicker than the other polymerlayers of the structure. This embodiment can, for example, stabilize theanode by allowing lithium ions to plate out more uniformly across thesurface of the anode during charge.

A polymer layer may be deposited by method such as electron beamevaporation, vacuum thermal evaporation, laser ablation, chemical vapordeposition, thermal evaporation, plasma assisted chemical vacuumdeposition, laser enhanced chemical vapor deposition, jet vapordeposition, and extrusion. The polymer layer may also be deposited byspin-coating techniques. A method for depositing crosslinked polymerlayers includes flash evaporation methods, for example, as described inU.S. Pat. No. 4,954,371 to Yializis. A method for depositing crosslinkedpolymer layers comprising lithium salts may include flash evaporationmethods, for example, as described in U.S. Pat. No. 5,681,615 toAfftnito et al. The technique used for depositing polymer layers maydepend on the type of material being deposited, the thickness of thelayer, etc.

As noted in the description with respect to FIG. 1 thus far, in oneparticular embodiment, the protective structure separating anode 20 fromelectrolyte 60 includes a polymer layer adjacent the anode (orseparation layer) 30. In other arrangements, a polymer layer need not bethe first layer adjacent the anode or separation layer. Variousarrangements of the invention, including various multi-layeredstructures, are described below in which the first layer adjacent theanode may or may not be polymeric. It is to be understood that in allarrangements where any particular arrangement of layers is shown,alternate ordering of layers is within the scope of the invention.Notwithstanding this, one aspect of the invention includes theparticular advantages realized by a non-brittle polymer immediatelyadjacent the anode or separation layer.

In some embodiments, multi-layered structures protect the anode betterthan any individual layer that is included in the structure. Forinstance, each of the layers of a multi-layered structure, e.g., thesingle-ion conducting layers, the polymer layers, or the separationlayer, may possess desirable properties, but at the same time may bemost effective when complemented by other components with differentproperties. For example, single-ion conducting layers, especially vacuumdeposited single-ion conducting layers, may be flexible as thin films,but when deposited as thicker layers, may include defects such aspinholes and/or roughness, and may crack when handled. Polymer layers,and especially crosslinked polymer layers, for example, can provide verysmooth surfaces, may add strength and flexibility, and may be electroninsulating, but may pass certain solvents and/or liquid electrolytes.Accordingly, these are examples of layers that can complement each otherin an overall improved protective structure.

Accordingly, in another embodiment, the invention provides amulti-layered electrode stabilization or protection structure thatprovides many advantages over existing electrode protective structures.In much of the description herein, the structure is referred to as an“anode stabilization” structure, but it is to be understood that thestructure can be used for any electrode under suitable conditions aswould be understood by those of ordinary skill in the art when takinginto consideration the function of a particular electrode. Multi-layeredelectrode stabilization structures of the invention, according to thisembodiment, are designed to minimize defects that might otherwise existinherently in prior electrode protective structures, or that might existinherently in electrode protective structures using the same or similarmaterials as those used in protective structures of the currentinvention, but arranged differently. For example, single ion-conductivelayers (or other components of a device as described herein) may includepinholes, cracks and/or grain boundary defects. Once these defects areformed, they can grow/propagate through the entire thickness of the filmas the film grows and may become worse as the film grows thicker. Byseparating thin single ion-conductive layers from each other with thin,pinhole free, smooth polymer layers, the defect structure in each singleion-conductive layer can be decoupled from the defect structure in everyother single ion-conductive layer by an intervening polymer layer. Thus,at least one or more of the following advantages are realized in such astructure: (1) it is less likely for defects in one layer to be directlyaligned with defects in another layer, and typically any defect in onelayer is substantially non-aligned with a similar defect in anotherlayer; (2) any defects in one single ion-conductive layer typically aremuch smaller and/or less detrimental than they would otherwise be in athicker layer of otherwise similar or identical material. Wherealternating single-ion conductive layers and polymer layers aredeposited atop each other in a fabrication process, each single-ionconductive layer has a smooth, pinhole free, polymer surface upon whichto grow. In contrast, where the single-ion conductive layer to bedeposited atop another single-ion conductive layer (or continuouslydeposited as a single, thicker layer), defects in an underlying layercan serve to instigate defects in growth in a layer deposited atop anunderlying layer. That is, whether a protective structure is built withthicker single-ion conductive layers or multiple single-ion conductivelayers atop each other, defects can propagate through the thickness, orfrom layer to layer, as the structure grows, resulting in largerdefects, and defects that propagate directly or substantially directlythroughout the entire structure. In this arrangement, the singleion-conductive layers can also grow with fewer defects than would occurif they were deposited directly onto the rougher Li or electrolytelayers, particularly where the arrangement of FIG. 1 is employed inwhich the first electrode stabilization layer addressing the electrodeis the polymer layer. Accordingly, in this arrangement, ion-conductivelayers can be made that have overall fewer defects, defects that are notaligned with defects in nearest other ion-conductive layers and, wheredefects exist, they are typically significantly less detrimental (e.g.,smaller) than would otherwise exist in a continuously-grown, thickerstructure or layers of the same or similar material deposited on top ofeach other.

A multi-layered electrode stabilization structure can act as a superiorpermeation barrier by decreasing the direct flow of species (e.g.,electrolyte and polysulfide species) to the Li anode, since thesespecies have a tendency to diffuse through defects or open spaces in thelayers. Consequently, dendrite formation, self discharge, and loss ofcycle life can be reduced.

Another advantage of a multi-layered structure includes the mechanicalproperties of the structure. The positioning of a polymer layer adjacenta single-ion conductive layer can decrease the tendency of thesingle-ion conductive layer to crack, and can increase the barrierproperties of the structure. Thus, these laminates may be more robusttowards stress due to handling during the manufacturing process thanstructures without intervening polymer layers. In addition, amulti-layered structure can also have an increased tolerance of thevolumetric changes that accompany the migration of lithium back andforth from the anode during the cycles of discharge and charge of thecell.

The ability of certain species that can be damaging to the anode (e.g.,electrolytes and/or polysulfides) to reach the anode can also bedecreased by providing repeated layers of single-ion conductive layersand polymer layers in a multi-layered structure. When a speciesencounters a defect-free portion of a single-ion conductive layer,transport of the species towards the anode is possible if the speciesdiffuses laterally through a very thin polymer layer to encounter adefect in a second single-ion conductive layer. Since lateral diffusionthrough ultra-thin layers is very slow, as the number of single-ionconductive/polymer layer pairs increases, the rate of diffusion ofspecies becomes extremely small (e.g., the amount of penetration acrossthe layer decreases). For instance, in one embodiment, permeation of aspecies through polymer/single-ion conductive/polymer 3-layer structurescan be reduced by three orders of magnitude over a single single-ionconductive layer alone (e.g., even though layers alone may have poorbarrier properties). In another embodiment, a polymer/single-ionconductive/polymer/single-ion conductive/polymer 5-layer structure mayhave more than five orders of magnitude reduction of permeation of aspecies compared to that in a single single-ion conductive layer. Bycontrast, permeation of the same species through a double-thicksingle-ion conductive layer may actually increase. These significantreductions in permeation of destructive species through the electrodestabilization layer can increase as the number of layers increases wherethe thickness of individual layers decreases. That is, in comparison toa two-layer structure of a single-ion conductive layer and polymer layerof a particular, overall thickness, a ten-layer structure of alternatingsingle-ion conductive layers and polymer layers of the same overallthickness can vary significantly decreased permeation of unwantedspecies through the layer. Specific arrangements are described below,and a principal involved in the increased barrier to passage of thesespecies is schematically illustrated below in FIG. 6. Because of thesignificant advantage realized by electrode stabilization protection ofthe invention, overall lower amounts of material can be used in aparticular protective structure, as compared to prior art structures.Accordingly, at a particular level of electrode protection needed in aparticular battery arrangement, a significantly smaller mass of overallelectrode stabilization materials can be employed, significantlyreducing overall battery weight.

A multi-layered structure can include various numbers ofpolymer/single-ion conductive pairs as needed. Generally, amulti-layered structure can have n polymer/single-ion conductive pairs,where n can be determined based on a particular performance criteria fora cell. E.g., n can be an integer equal to or greater than 1, or equalto or greater than 2, 3, 4, 5, 6, 7, 10, 15, 20, 40, 60, 100, or 1000,etc. In some embodiments, a multi-layered structure can include greaterthan 4, greater than 10, greater than 25, greater than 50, greater than100, greater than 200, greater than 500, greater than 1000, greater than2000, greater than 3000, greater than 5000, or greater than 8000polymer/single-ion conductive pairs. For example, in one particularembodiment, greater than 10,000 polymer/single-ion conductive pairs werefabricated.

FIG. 2 shows an example of a multi-layered electrode stabilizationstructure including multiple polymer and single-ion conductive layers.In the embodiment illustrated in FIG. 2, structure 11 includes anode 20comprising a base electrode material (e.g., lithium), and multi-layeredstructure 24 positioned between the anode and an electrolyte 60 of thecell. The multi-layered structure comprises at least two first layerseach of a single-ion conductive material and at least two second layerseach of a polymeric material. For example, multi-layered structure 24includes polymer layers 40 and 42, and single-ion conductive layers 50and 52. As shown in FIG. 2, the two layers of polymeric material and twolayers of single-ion conductive material are arranged in alternatingorder with respect to each other. Structure 11 may optionally comprise aseparation layer (e.g., a plasma treated layer) between the baseelectrode material and the polymeric layer (not shown in FIG. 2;illustrated in FIG. 1).

Structure 11 can also include additional multi-layered structures suchas multi-layered structure 26, comprising polymer layers 44 and 46, andsingle-ion conductive layers 54 and 56. Multi-layered structures 24 and26 can be combined to form a single multi-layered, or can be constructedtogether as one, unitary multi-layered structure, including four layerseach of a single-ion conductive material and for layers each of apolymeric material. In other embodiments, structures can include othernumbers of alternating single-ion conductive layers and polymer layers.For instance, a multi-layered structure may include n first layers eachof a single-ion conductive material and n second layers each of apolymeric material, in alternating arrangement, where n is greater thanor equal to 2. E.g., n may equal at least 2, 3, 4, 5, 6, or 7, 10, 15,20, 40, 60, 100, etc.

In other embodiments, a multi-layered structure may include a greaternumber of polymer layers than single-ion conductive layers, or a greaternumber of single-ion conductive layers than polymer layers. For example,a multi-layered structure may include a n polymer layers and n+1single-ion conductive layers, or n single-ion conductive layers and n+1polymer layers, where n is greater than or equal to 2. E.g., n may equal2, 3, 4, 5, 6, or 7, etc. However, as described above, it is immediatelyadjacent at least one polymer layer and, in at least 50%, 70%, 90%, or95% of the ion-conductive layers, such layers are immediately adjacent apolymer layer on either side.

As mentioned, multi-layered electrode stabilization structures canprovide significant advantage where a particular amount of materialsdefining the structure are arranged in thinner, and greater numbers of,form. In some embodiments, each layer of the multi-layered structure hasa maximum thickness of less than 100 microns, less than 50 microns, lessthan 25 microns, less than 10 microns, less than 1 micron, less than 100nanometers, less than 10 nanometers, or less than 1 nanometer.Sometimes, the thickness of a single type of layer may be the same in amulti-layered structure. For instance, polymer layers 40 and 42 may havethe same thickness in multi-layered structure 24. In other embodiments,the thickness of a single type of layer may be different in amulti-layered structure, e.g., polymer layers 40 and 42 may havedifferent thicknesses in multi-layered structure 24. The thicknesses ofdifferent types of layers in a multi-layered structure may be the samein some cases, or different in other cases. For example, the thicknessesof polymer layers 40 and 42 may be different than the thickness ofsingle-ion conductive layers 50 and 52. Those of ordinary skill in theart can select appropriate materials and thicknesses of layers incombination with the description herein.

A multi-layered structure may have various overall thicknesses that candepend on, for example, the electrolyte, the cathode, or the particularuse of the electrochemical cell. In some cases, a multi-layeredstructure can have an overall thickness of less than or equal to 1 cm,less than or equal to 5 mm, less than or equal to 1 mm, less than orequal to 700 microns, less than or equal to 300 microns, less than orequal to 250 microns, less than or equal to 200 microns, less than orequal to 150 microns, less than or equal to 100 microns, less than orequal to 75 microns, or less than or equal to 50 microns. It may also bedesirable to have a multi-layered structure having a certain thicknesswith a certain number of polymer/single-ion conductive material pairs.For instance, in one embodiment, a multi-layered structure may have athickness of less than 1 mm, and may include greater than 10polymer/single-ion conductive material pairs. In another embodiment, amulti-layered structure may have a thickness of less than 0.5 mm, andmay include greater than 50 polymer/single-ion conductive materialpairs. It is to be understood that a variety of embodiments are providedby the invention, each including specific combinations of overallelectrode stabilization thickness, thicknesses of individual layers,numbers of individual layers, etc. as described herein.

As noted, multi-layered structures can protect the anode by decreasingwater and/or oxygen penetration across the layers. For instance, atypical PVD oxide coating of a few hundred Angstroms thick on 12 micronthick PET surface can decrease water and/or oxygen permeation by afactor of 30-40 times compared to a surface without the PVD oxidecoating. The water and/or oxygen permeation decrease resulting from atypical 1 micron thick acrylate coating (coated monomer that issubsequently polymerized) on a 12 μm thick PET surface may be barelymeasurable. However, applying the acrylate coating over the oxide layerin the PET/oxide structure can result in a further 10-20 fold decreasein water and/or oxygen permeation. Two polymer/oxide pairs can decreasewater and/or oxygen permeation by more than 100 fold over a single PVDoxide coating, while 5 pairs can reduce oxygen permeation by more than 5orders of magnitude. As such, electrochemical cells includingmulti-layered structures are well-suited for use in water and/or oxygenor air environments.

Another embodiment of the invention includes an embedded layer (e.g., ofa single-ion conductive material) positioned between two layers of baseelectrode materials. This is referred to as a “lamanode” structure. FIG.3 shows structure 12 including anode 20 comprising a first layer of abase electrode material (e.g., lithium, also referred to as a Lireservoir), embedded layer 70, and a second layer 22 comprising the baseelectrode material (a working Li layer). As illustrated in theembodiment shown in FIG. 3, the second layer is positioned between theanode 20 and electrolyte 60. The second layer may be either in directcontact with the electrolyte, or in indirect contact with theelectrolyte through some form of a surface layer (e.g., an electrodestabilization structure, for example, one described herein). Thefunction of the bi-layer anode structure, with each anode portionseparated by an imbedded layer 70, will become clearer from thedescription below. It is noted that although layer 70 is illustrated anddescribed as “embedded” in this description, it is noted that the layerneed not be partially or fully embedded. In many or most cases, layer 70is a substantially thin, two-sided structure coated on each side byanode material, but not covered by anode material at its edges. Ingeneral, in operation of the arrangement shown in FIG. 3, some or all ofsecond layer (portion) 23 of the anode is “lost” from the anode upondischarge (when it is converted to lithium ion which moves into theelectrolyte). Upon charge, when lithium ion is plated as lithium metalonto the anode, it is plated as portion 23 (or at least some portion ofportion 23) above layer 70. Those of ordinary skill in the art are awarethat in batteries such as those described herein, there is a smallamount of overall lithium loss on each charge/discharge cycle of thebattery. In the arrangement illustrated in FIG. 3, the thickness oflayer 23 (or the mass of layer 23) can be selected such that most or allof layer 23 is lost upon full discharge of the battery (full“satisfaction” of the cathode; the point at which the cathode can nolonger participate in a charging process due to limitations that wouldbe understood by those of ordinary skill in the art). Layer 70 isselected to be one that is conductive to lithium ions. The embeddedlayer can shield the bottom Li layer from damage as the high Li⁺ flux ofthe first cycle damages the top Li layer surface. Accordingly, once allof layer 23 is consumed in a particular discharge cycle, furtherdischarge results in oxidation of lithium from layer 21, passage oflithium ion through layer 70, and release of lithium ion into theelectrolyte. Of course, layer 23 need not be of a particular mass suchthat all or nearly all of it is consumed on first discharge. It may takeseveral discharge/charge cycles, and inherent small amount of lithiumloss through each cycle, to result in the need to draw lithium fromsection 21 through layer 70 and into the electrolyte. But once thatoccurs, then each subsequent charge/discharge cycle will generallyprogress as follows.

Through most of the discharge cycle lithium will be removed from section23 and, at the very end of the discharge cycle, a small amount oflithium will be required to be drawn from section 21 through layer 70 tomake up for the amount of lithium lost in the most recentcharge/discharge cycle. Upon charge, lithium will be plated upon layer70 as material 23 in an amount very slightly less than that removed fromthe anode during discharge. The electrode stabilization layer 70 can bemade of any suitable material selected, by those of ordinary skill inthe art, in accordance with the function described herein. Generally,layer 70 will be made of a material that is single-ion conductive butthat will not allow lithium metal itself to pass. In some embodimentsthe material is non-electrically-conductive, for reasons describedbelow.

The ratio of the thickness of first and second layers of base electrodematerials can be calculated based on, e.g., a required “depth ofdischarge” (amount of lithium metal consumed) of the first discharge.The ratio may be, for instance, between the range of 0.2 to 0.4. Thethickness of anode 20 may be, for instance, less than 100 microns, lessthan 50 microns, less than 25 microns, or less than 10 microns. In someembodiments, anode 20 can have a thickness between 10 and 30 microns.

In some embodiments, embedded layer 70 may have a thickness between0.01-1 microns, and may depend on, e.g., the type of material used toform the embedded layer and/or the method of depositing the material.For example, the thickness of the embedded layer may be between 0.01-0.1microns, between 0.1-0.5 microns, or between 0.5-1 micron. In otherembodiments, thicker embedded layers are included. For example, theembedded layer can have a thickness between 1-10 microns, between 10-50microns, or between 50-100 microns. In some cases, the embedded materialcan be formed of a polymer, e.g., including ones listed above that arelithium ion conductive. The polymer film can be deposited usingtechniques such as vacuum based PML, VMT or PECVD techniques. In othercases, an embedded layer can comprise a metal or semi-conductormaterial. Metals and semi-conductors can be, for example, sputtered.Those of ordinary skill in the are can choose suitable materials,thicknesses, and methods of depositing embedded layers based on routineexperimentation in combination with disclosure herein.

In one embodiment, layer 70 is an anode stabilization structure ofmulti-layer form as described above in connection with FIG. 2 and asdescribed more fully below.

The second layer 23 of lithium can be used to protect the surface ofanode 20 (e.g., a Li surface) by limiting the current density-inducedsurface damage to a thin Li layer above the embedded layer 70. Forinstance, layer 23 can lithiate the cathode (be removed from the anodein the form of lithium ion) on the first cycle, e.g., under extremelyhigh Li⁺ flux, instead of causing anode 20 to lithiate the cathode,thereby protecting anode 20. In each charge/discharge cycle (after thepoint is reached at which more lithium than is present in layer 23 isremoved from the anode during discharge) only a small amount of lithiumis removed from section 21 and no lithium is re-plated at section 21.This can eliminate or reducing the numbers of defects, cracks, pinholesand/or dendrites forming on the surface of anode 20 during the cathodelithiation. Structure 12 can improve the cycle life of the cell comparedto a cell including an anode without a second layer of Li and/or anembedded layer, as described in further detail below.

As mentioned, layer 70 should be able to pass lithium ions. It can bemade of material including ceramic, glass, or polymer layer (or amulti-layered structure, as described below) that is conductive to Liions and, in some embodiments, it substantially impedes the passage ofelectrons across the layer. By “substantially impedes”, in this context,it is meant that in this embodiment the material allows lithium ion fluxat least ten times greater than electron passage. As noted, in otherembodiments the material can be electron conductive.

Referring again to FIG. 3, anode 12 can function with any of a varietyof current collectors (not shown). Current collectors are well known tothose of ordinary skill in the art and can be readily selected fromsuitable materials based upon this disclosure. In one arrangement, acurrent collector addresses the bottom surface of section 21 of anode 20(the side opposite electrolyte 60). In another arrangement, an edgecollector is used, which can be positioned on one or multiple edges,i.e., a side, as illustrated in FIG. 3, including section 21, material70, and section 23. In other arrangements, both a bottom collector andone or more edge collectors can be used. Where only a bottom collectoris used, material 70 should be electronically conductive as well aslithium ion conductive. Where an edge collector is used material 70 canbe selected to substantially inhibit electron passage.

In one particular set of embodiments, an edge collector is used andprovides advantage in anode stabilization/protection. One sucharrangement is illustrated in FIG. 4, where an embedded stabilizationstructure 24 (itself analogous to section 70 of FIG. 3), separates theLi anode 20 into one portion 21, (the Li reservoir), from a secondportion of Li, layer 23 (the working Li layer). The embedded layer,e.g., multi-layered structure 24, the Li reservoir, and layer 22 can allbe electrically connected at the edge current collector 80. In thearrangement illustrated in FIG. 4, a bottom current collector is notused.

During operation of an electrochemical cell as illustrated in FIG. 4, oranother cell including an embedded layer between two base electrodematerial layers and with an edge collector, during discharge, currententers the anode through the working Li/electrolyte interface. However,the embedded layer can substantially block electron current whileallowing passage of Li ions. For instance, the flow of electron current,as illustrated by the arrows in FIG. 4, may be substantially impededthrough the electrode stabilization layer, to section 21 of the anode,and to one or more current collectors. Thus, a substantial amount orsubstantially all of the current can pass through the working Li layer23 to the edge collector 80, e.g., in the direction of arrow 84, while amuch smaller portion (or essentially no electron flow) passes throughstabilization material 24 to the Li reservoir 21 to the edge collector,e.g., in the direction of arrows 82 and 89, or to a bottom currentcollector (not shown) in the direction of arrows 86 and 88. As noted, insome embodiments, the working Li layer, prior to first discharge of thecell 23, comprises more active electrode species than is depleted uponfull discharge of the counter electrode, e.g., as to satisfy the cathodeupon cathode lithiation. E.g., the working Li layer may include anamount of Li, prior to first discharge of the cell, such that greaterthan 50%, greater than 70%, greater than 90%, or greater than 95% of theLi of the working layer 23 is electrochemically dissolved upon the firstdischarge.

On charging, lithium ion is plated, as lithium metal, at the anode, asdescribed above in connection with FIG. 3. Since the electrolyte/workingLi layer 23/edge collector 80 is the lowest resistance path for electroncurrent, most current takes this path once Li ion reaches the working Lilayer and is reduced. Current density induced damage/corrosion issignificantly minimized since any such processes occur only or primarilyat the electrolyte/working Li 23 interface, while the embedded layer 21remains undamaged. As noted above in connection with FIG. 3, as theworking Li layer gradually loses a small percentage of Li during eachcycle, this Li is replaced by a flow of Li ions across the embeddedlayer 24 and into the electrolyte. This results in more evenloss/re-plating of lithium during discharge/charge cycles, thereforeminimizing damage/corrosion of the anode and, importantly, thedamage/corrosion can be inhibited or made to be essentially zero in Lireservoir 21. As a result, the Li reservoir does not degenerate intoisolated Li islands surrounded by corrosion byproducts, as can be thecase with use of a single layer Li anode.

A variety of arrangements can be employed to encourage even plating oflithium at section 23 during charge. For example, although in theembodiment illustrated in FIG. 4 it can be advantageous to form layer 24to be substantially non-electrically conductive overall, one or morelayers of the structure can be made to be electrically conductive todefine a current collector component. For example, in structure 24 oneor more of the layers, for example layer 52 closest to section 23 andelectrolyte 60, can be made somewhat or significantly electricallyconductive. In this way, during charge, even deposition of the firstvery thin layer of lithium on the anode can be made to occur essentiallyevenly across structure 24. Once a portion of lithium has beendeposited, then the electronic conductivity of lithium itself alsofacilitates further even deposition of material 23.

Structures such as those shown in FIGS. 3 and 4 may be used with primaryor secondary cells. In some cases, a method of electrical energy storageand use may include alternately discharging current from the cell todefine an at least partially discharged device, and at least partiallycharging said at least partially discharged device to define an at leastpartially recharged device. This discharge and charge may cause the baseelectrode material from a working Li layer (e.g., layer 23 of FIG. 4) tobe consumed upon discharge to a greater extent than it is re-plated uponcharge, which can cause the base electrode material to be replenishedinto the working Li layer, from the base anode layer (e.g., layer 21 ofFIG. 4), across the embedded layer. Such cells can operate in thepresence of an aqueous (e.g., water) or air electrolyte inelectrochemical communication with the anode and cathode.

When a rechargeable lithium battery using an aqueous electrolyte, orother primary or secondary electrochemical device described herein oruseful in connection with components of the invention, is constructed bythose of ordinary skill in the art, one or many of the featuresdescribed herein can be employed. For example, a device can include anelectrode stabilization component 22 as shown in FIG. 1. In anotherarrangement a device can include a stabilization component 70 asillustrated in FIG. 3. In another arrangement a multi-layered electrodestabilization structure, such as described in connection with FIG. 2,can be used as shown in FIG. 4 in combination with one or more ofhydrophobic materials inhibiting passage of water and/or a basic (pHgreater than 7.1, or higher) aqueous electrolyte. Combinations or one ormore of these structures can result in a significantly robustaqueous-based lithium rechargeable battery, and the battery may also becompact and/or light weight (e.g., the total thickness of the layersbetween and including the anode and an outer layer may be less than 1cm, less than 0.5 cm, less than 1 mm, less than 700 microns, less than500 microns, less than 300 microns, less than 250 microns, less than 200microns, less than 150 microns, less than 100 microns, less than 75microns, less than 50 microns, or less than 10 microns). As such, theinvention enables a method of electrical energy storage and useincluding providing an electrochemical cell comprising an anode withlithium as the active anode material, a cathode, and an aqueouselectrolyte in electrochemical communication with the anode and cathode,and cycling the cell, by alternately discharging and charging the cell,at least n times wherein, at the end of the nth cycle, the cell exhibitsat least 80% of the cell's initial capacity, where n=at least 3, 5, 10,15, 25, 50, 100, 150, 200, or 250 or more. As noted, the invention canbe used to enhance the lifetime of rechargeable lithium batteriesemploying aqueous-based electrolytes. As used herein, “aqueous-basedelectrolyte” means an electrolyte including at least 20%, by weight,water, and more typically at least 50%, 70%, 80%, or 95% or more waterby weight. Several additional features are included in the invention toassist function in a rechargeable battery useful in an aqueousenvironment, or an environment exposed to air. In the case of anaqueous-based electrolyte, in one set of embodiments the electrolyte isformulated so as to have a pH of at least 7.1, and in other embodimentsat least 7.2, 7.3. 7.4., 7.5, 7.6, 7.7, or 7.8 providing an electrolytein basic form such as this inherently significantly reduces the presenceof hydrogen ion which can be destructive if exposed to a lithium orother alkali metal electrode. In some embodiments, the electrolyte mayhave a pH between 7-8, between 8-9, between 9-10, between 10-11, orbetween 11-12 prior to the first discharge.

Formulating an electrolyte in basic form can be carried out by those ofordinary skill in the art, without undue experimentation, whileproviding the electrolyte with the ability to function effectively inthe device and not causing inhibitory or other destructive behavior.Suitable basic species that may be added to an aqueous-basedelectrolyte, employed with a lithium battery, to achieve a basic pH asnoted above may depend on, for example, the specific components of thelithium battery, the environment of use (e.g., an air/oxygen or waterenvironment), the method of using the battery (e.g., a primary orsecondary battery), etc. Suitable basic species may also be chosen basedon the basicity (e.g., pH) of the species, the diffusivity of thespecies, and/or the likelihood of the species reacting with theelectrolyte, other components in the electrolyte, components of theanode (e.g., polymer layers, single ion conductive layers, and anodelayers), and/or the cathode material. Typically, chemical reactionbetween the basic species and such components of the battery areavoided. Accordingly, those of ordinary skill in the art can choose anappropriate basic species by, e.g., knowing the components of thebattery and the likelihood of reactivity between the species and thecomponents, and/or by a simple screening test. One simple screening testmay include adding the species to the electrolyte in the presence of amaterial component of the cell, e.g., a single-ion conductive material,and determining whether the species reacts and/or negatively effects thematerial. Another simple screening test may include adding the speciesto the electrolyte of the battery in the presence of the batterycomponents, discharging/charging the battery, and observing whetherinhibitory or other destructive behavior occurs compared to that in acontrol system. Other simple tests can be conducted by those of ordinaryskill in the art.

Species that may be added to an aqueous-based electrolyte, employed witha lithium battery, to achieve a basic pH as noted above include basescomprising alkali and alkali earth metals (Group 1 and 2 metals,respectively), as well as ammonium-containing species (e.g., ammoniumhydroxides, carbonates, and sulfides). Specific examples of species thatcan be added to an aqueous-based electrolyte to achieve a basic pHinclude, but are not limited to, ammonia, aniline, methylamine,ethylamine, pyridine, calcium carbonate, calcium hydroxide, ferroushydroxide, potassium acetate, potassium bicarbonate, potassiumcarbonate, potassium cyanide, potassium hydroxide, sodium acetate,sodium benzoate, sodium bicarbonate, sodium carbonate, sodium hydroxide,sodium metasilicate, sodium sesquicarbonate, sodium phosphate, sodiumhydrogen phosphate, sodium sulfite, sodium cyanide, trisodium phosphate,magnesium hydroxide, barium hydroxide, calcium hydroxide, lithiumhydroxide, rubidium hydroxide, cesium hydroxide, and strontiumhydroxide. It is routine for those of ordinary skill in the art todetermine the amount of such an additive needed to create an electrolyteof desired pH.

In another arrangement suitable for maximizing the effectiveness of analkali metal electrode-containing device used in combination with anaqueous-based electrolyte, especially a rechargeable battery, theelectrode stabilization/protective component (e.g., as illustrated inFIGS. 1 and 2, and optionally FIGS. 3 and 4) can be made to besubstantially impermeable to water. This can be done by selecting one ormore materials that are sufficiently hydrophobic or otherwise impedewater transport. This concept will be described, by way of example only,with reference to FIG. 2. In FIG. 2, one effective device will include atop layer (layer 56 as illustrated) that is significantly hydrophobic soas to prevent water passage. In another arrangement, an intermediatelayer (e.g., 44, 52, 42, etc.) can be made sufficiently hydrophobic toblock water passage. In another arrangement, none of the layersindividually is sufficiently hydrophobic or otherwise formulated tosubstantially prevent water passage but, together the layerssubstantially prevent water passage. For example, each layer, or somecombination or subcombination of layers, can be made somewhathydrophobic so that each repels water to some extent. In thisarrangement, the combination of the layers can be formulated and/orselected to substantially prevent water passage overall. One measure ofhydrophobicity that can be useful in selecting such materials is contactangle measurements taken between water and a candidate material. While“hydrophobic” can be considered a relative term in some cases, aparticular degree or amount of hydrophobicity can be easily selected bythose of ordinary skill in the art, with the aid of knowledge of thecharacteristics of particular materials and/or readily-determinedcontact angle measurements to select materials for construction of ananode stabilization structure which, overall, impedes water passagesignificantly. “Significantly” in this context, can mean that where anaqueous electrolyte is used, after 100 cycles of a rechargeable deviceemploying the stabilization component water will be completely absentfrom the electrode under the stabilization component (the side oppositethe electrolyte) or, if present, will be present in an amount less than100 parts per million measured to include all molecular species at thatlocation. In other embodiments, water will be present in an amount lessthan 75 ppm, less than 50, 25, 10, 5, or 2 ppm.

A variety of materials and arrangements can be used in individualassemblies described and illustrated herein, or in all of theassemblies. It is to be understood that where a particular component orarrangement is described in connection with one embodiment or figure,that component or arrangement can be used in connection with any others.One example of such a structure is a separation layer, e.g., a temporaryprotective material layer or a plasma CO₂ treatment layer, positionedbetween the an anode layer and a polymer layer or a multi-layeredstructure. For example, in the embodiments shown in FIG. 1, layer 30 isa separation layer. It is to be understood that where a separation layer30 is used, the first layer adjacent the separation layer opposite theelectrode is described herein at times to be adjacent the electrode.This is because the separation layer is optional. In all instances inwhich a layer is described as being adjacent, or immediately adjacent anelectrode (for example the polymer layer 40 of FIG. 1), an interveningseparation layer can be used but need not be used. Separation layers mayimprove the compatibility of the base electrode material (e.g., lithium)with layers deposited on top of the electrode. For example, when asingle-ion conductive layer is desired at the lithium interface, it ispreferable to deposit this directly on the lithium surface. However, theprecursors to, or components of, such an interfacial layer may reactwith lithium to produce undesirable by-products or result in undesirablechanges in the morphology of the layers. By depositing a separationlayer on the lithium surface prior to depositing the interfacial layersuch as a multi-layer structure 24 (FIG. 2), side reactions at thelithium surface may be eliminated or significantly reduced. For example,when an interfacial film of a lithium phosphorus oxynitride, asdescribed in U.S. Pat. No. 5,314,765 to Bates, is deposited in anitrogen atmosphere by sputtering of Li₃PO₄ onto a lithium surface, thenitrogen gas may react with lithium to form lithium nitride (LiN₃) atthe anode surface. By depositing a layer of a protective material thatcan be “temporary”, e.g., copper over the lithium surface, theinterfacial layer may be formed without the formation of lithiumnitride. A “temporary” protective layer is one that ceases to be inexistence or identifiable after some time after construction of thedevice, for example after some period of use of the device. For example,a thin layer of copper 30 positioned over a lithium anode 20 (describedin the context of FIG. 1) will diffuse into an alloy with the anodeuntil, after a particular period of time and/or use of the device, anode20 will be primarily lithium, with a trace of copper, but layer 30 willno longer exist or be identifiable.

A temporary protective material layer may include a material that iscapable of forming an alloy with lithium metal, or is capable ofdiffusing into, dissolving into, and/or blending with lithium metal,e.g., during electrochemical cycling of the cell and/or prior toelectrochemical cycling of the cell. The temporary protective materiallayer can act as a barrier layer to protect the lithium surface duringdeposition of other layers, such as during the deposition of amulti-layered structure on top of the anode. Further, the temporaryprotective layer may allow transportation of the lithium films from oneprocessing station to the next without undesirable reactions occurringat the lithium surface during assembly of cells, or for solvent coatingof layers onto the anode.

The thickness of the temporary protective material layer is selected toprovide the necessary protection to the layer comprising lithium, forexample, during subsequent treatments to deposit other anode or celllayers. In some embodiments, it is desirable to keep the layer thicknessas thin as possible while providing the desired degree of protection soas to not add excess amounts of non-active materials to the cell whichwould increase the weight of the cell and reduce its energy density. Inone embodiment, the thickness of the temporary protective layer isbetween 5 to 500 nanometers, e.g., between 20 to 200 nanometers, between50 to 200 nanometers, or between 100 to 150 nanometers.

Suitable materials that can be used as temporary protective materiallayers include metals such as copper, magnesium, aluminum, silver, gold,lead, cadmium, bismuth, indium, gallium, germanium, zinc, tin, andplatinum.

In some cases, protective structure 30 can include plasma treated layerssuch as CO₂ or SO₂ induced layers. Plasma treated layers can allownearly the entire anode surface area to participate in the currentcarrying process. In other words, plasma treated layers may allowuniform current density across a surface and decreases the amount ofpitting on a surface. In some cases, these treatments alone routinelyincrease cycle life by 15% to 35% because more of the Li is availablefor use during discharge. The plasma surface treatments can make more ofthe Li available to be cycled by creating a surface that issubstantially homogeneous in topography.

FIG. 5 illustrates the results of one comparative experiment showing thebenefits of a temporary protective layer 30, which can be used incombination with any or all other features of the invention. FIG. 5shows SEM images of Li anode surfaces after a 10^(th) discharge. FIGS.5A-5C show images of a Li anode alone without plasma treatment throughprogressive use of the device. The spots are areas where Li has beencorroded from the surface. FIGS. 5D-5F show anode surfaces treated witha layer of LiPON through progressive use, comparative to FIGS. 5A-5C.With these surfaces, the Li only corrodes under defects in the LiPONcoating. FIGS. 5G-5I show anode surfaces that have been treated with aCO₂ plasma, again through progressive use comparative to that of FIGS.5A-5C and FIGS. 5D-5F. These images show that a substantial portion ofthe anode surface was utilized during discharge, indicating lowercurrent discharge density across the surface and increased cycle life.

Another example of a structure that can be used in connection withseveral embodiments of the invention include single-ion conductivelayers (e.g., as part of a multi-layered structure) that are treatedwith a transport-inhibiting substance which can be a polymer or otherspecies such that any nanopores and/or pinholes of the single-ionconductive layer are at least partially filled with the polymer. Thisfilling creates an infiltrated porous barrier (IPBM), which can increasethe barrier properties of the layer by decreasing the rate of transportof certain species (e.g., electrolyte, water, and oxygen) towards theanode.

Advantageously, the filled single-ion conductive layer can have acombination of low permeability and high flexibility, due to theresultant network of infiltrating transport-inhibiting substance. Thehigher elastic modulus of such a species, when a polymer is selected,relative to the brittle compounds that may be used for the single-ionconductive layer can provide flexibility in the IPBM, as well as aresistance to fracture, that is not possible with certain single-ionconductive materials. Polymers having physical characteristics asdescribed elsewhere herein can be used for such infiltrating species.This flexibility without fracture may improve adhesion between theinfiltrated polymer and the internal surfaces of the single-ionconductive material is increased due to the high surface energy of thesingle-ion conductive material prior to infiltration.

In one embodiment, a single-ion conductive layer is infiltrated with amonomeric precursor of the transport-inhibiting substance, so that theporous structure is effectively filled with the monomer, the monomerbeing driven into the nanoporous regions of the porous single-ionconductive layer by the high surface energy present on the single-ionconductive layer's internal surfaces. The single-ion conductive materialmay be treated with an activation process before treatment with themonomer, so that surface energy within the material becomes unusuallyhigh, relative to that achievable in normal atmospheric processes.

In some instances, monomer vapor can be condensed onto the single-ionconductive material layer, whereby it is then able to wick along theinternal surfaces of the single-ion conductive material layer, untilall, or some useful portion of, such available tortuous by-paths ofpermeation are filled by the monomer. A subsequent curing step, eitherphoto-initiated techniques, plasma treatment, or an electron beam, canthen be introduced for polymerization of the infiltrated monomer. Theparticular cure method utilized will depend on the specific choice ofmaterials and the layer thickness, amongst other variables.

Suitable material used as the transport-inhibiting substance includesmaterial known to fully or partially inhibit (or determined to inhibitthrough simple screening) transport of a particular unwanted speciesthrough the material. As mentioned, material may also be selectedaccording to physical properties, including properties addingflexibility and/or strength to the overall material with which it iscombined. Specific examples of materials include, as noted, polymersdescribed herein for use as layers in the multi-layered structure,and/or other polymeric or other species. Where hydrophobicity isdesirably added to the overall arrangement, one way to do so is to usean infiltrating transport-inhibiting substance having some degree ofhydrophobic character.

Formation of IPBM-type structures may be accomplished by a variety ofmeans; however, in some embodiments, the IPBM is formed by vacuum vapordeposition methods and apparatus readily available in prior artmanufacturing processes. Accordingly, an IPBM may be formed utilizing avariety of prior art vapor sources for the IPBM material. The inorganicvapor source may comprise any appropriate source of the prior art,including but not limited to sputtering, evaporation, electron-beamevaporation, chemical vapor deposition (CVD), plasma-assisted CVD, etc.The monomer vapor source may similarly be any monomer vapor source ofthe prior art, including but not limited to flash evaporation, boatevaporation, Vacuum Monomer Technique (VMT), polymer multilayer (PML)techniques, evaporation from a permeable membrane, or any other sourcefound effective for producing a monomer vapor. For example, the monomervapor may be created from various permeable metal frits, as previouslyin the art of monomer deposition. Such methods are taught in U.S. Pat.No. 5,536,323 (Kirlin) and U.S. Pat. No. 5,711,816 (Kirlin), amongstothers.

A separate activation may be utilized in some cases for providingadditional activation energy during or after deposition of thesingle-ion conductive material layer. In some cases, such as in certaintypes of unbalanced magnetron sputtering, plasma immersion, orplasma-enhanced CVD, a separate activation source may not be required,as the sufficient activation is already attained by the depositionmethod itself. Alternatively, certain types of single-ion conductivematerials, such as those that provide catalytic or low work functionsurfaces, e.g., ZrO₂, Ta₂O₅, or various oxides and fluorides of Group IAand Group IIA metals, may provide sufficient activation even inrelatively non-activating deposition processes.

Not all of the surface area within a single-ion conductive materiallayer need be infiltrated by the transport-inhibiting substance toachieve an effective permeation barrier. Accordingly, it is not requiredthat all of the pores within the single-ion conductive material layer befilled. In some cases, less than 10%, less than 25%, less than 50%, lessthan 75%, or less than 90%, of the pores and/or pinholes can be filledwith a polymer, e.g., to achieve decrease in permeation of certainspecies across the layer. In some cases, the advantages described abovecan be obtained so long as those pores that substantially contribute topermeation are substantially filled by the polymer.

Other advantages and methods of forming filled single-ion conductivelayers are discussed in U.S. Patent Application No. 2005/0051763(Affinito).

FIG. 6 illustrates a principle behind use of a multi-layer electrodestabilization component, such as illustrated in FIGS. 2, 4, and 7, withfilled nanopores/pinholes and illustrating the significant barrier topassage of unwanted components from electrolyte to anode through theelectrode stabilization layer. In the figure, a tortuous pathwayrepresented by arrow 71 is presented by way of example to show thesignificant distance, and tortuosity, through which such a species wouldneed to pass to penetrate the entire multi-layer arrangement to arriveat the anode. Where nanopores and pinholes are filled with a penetratingtransport-inhibiting substance such as an inhibiting polymericsubstance, transport is significantly slowed. This, combined withtortuosity as illustrated, can result in the exponential decrease intransport of such species and exponential increase in cycle life, asnoted above. It can be seen how increasing the number of layers, withresultant offset of pinholes existing in ion-conductive materials,creates this tortuous pathway. Where a single layer of such material isused, pinholes can be substantially more easily traversed by unwantedspecies accessing the electrode. In certain embodiments, thetransport-inhibiting substance fills essentially all voids includingpinholes and nanopores of the single ion-conducting material, and/orthat of the polymer layers. In other arrangements, only a portion ofvoids of one or both are filled. In some cases, the transport-inhibitingsubstance is an auxiliary substance, that is, a substance not native tothe single ion-conducting material, and/or that of the polymer layers.That is, the material may be a species not forming a portion of one ofthese components as these components would otherwise be fabricated andassembled together, but is present only through an auxiliary processrequired to fill such voids. In some cases, the material is not nativeto either the single-ion conductive material or the polymeric material.

In some embodiments, structures include an outer layer, e.g., a layerthat is in contact with the electrolyte of the cell. This outer layercan be a layer such as stabilization layers 22, 24, 26, etc. as shown inthe figures, or can be an auxiliary outer layer specifically selected tointerface directly with the electrolyte. Where such an auxiliary outerlayer is used, it may be selected to be significantly hydrophobic whenused in connection with an aqueous electrolyte and a rechargeablelithium battery. Outer layers may be selected for properties such asLi-ion conduction, electron conduction, protection of underlying layerswhich may be unstable to components present in the electrolyte,nonporous to prevent penetration by electrolyte solvents, compatiblewith electrolyte and the underlying layers, and flexible enough toaccommodate for volume changes in the layers observed during dischargeand charge. The outer layer should further be stable and preferablyinsoluble in the electrolyte.

Examples of suitable outer layers include, but are not limited to,organic or inorganic solid polymer electrolytes, electrically andionically conducting polymers, and metals with certain lithiumsolubility properties. In one embodiment, the polymer of the outer layeris selected from the group consisting of electrically conductivepolymers, ionically conductive polymers, sulfonated polymers, andhydrocarbon polymers. Further examples of suitable polymers for use inthe outer layer of the present invention are those described in U.S.Pat. No. 6,183,901 to Ying et al.

As noted, structures may further comprise a substrate, on a surface ofan anode layer, e.g., on a side opposite to that of a multi-layerstructure. Substrates are useful as a support on which to deposit thefirst layer comprising the base electrode material, and may provideadditional stability for handling of thin lithium film anodes duringcell fabrication. Further, in the case of conductive substrates, thesemay also function as a current collector useful in efficientlycollecting the electrical current generated throughout the anode and inproviding an efficient surface for attachment of the electrical contactsleading to the external circuit. A wide range of substrates are known inthe art of anodes. Suitable substrates include, but are not limited to,those including metal foils, polymer films, metallized polymer films,electrically conductive polymer films, polymer films having anelectrically conductive coating, electrically conductive polymer filmshaving an electrically conductive metal coating, and polymer filmshaving conductive particles dispersed therein.

FIG. 7 shows an example of a structure including several embodimentsdescribed herein. As illustrated in the embodiment shown in FIG. 7,structure 14 can include a substrate 96 and a layer 20 (e.g., based onor essentially completely comprising lithium metal). A separation layer30, which may include a plasma treated layer or a temporary metal layer,may be formed on top of base anode layer 21. The structure may include asecond lithium layer 23, and an embedded layer 72 comprising, e.g.,alternating polymer layers 40 and 42, and single-ion conductive layers50 and 52. In some embodiments, the single-ion conductive materiallayers may comprise, or consist essentially of, a metal. The single-ionconductive layers material may be an IPBM-type structure, e.g., a layerin which the nanopores/pinholes are filled with a suitable polymer todecrease permeation of the layer. A second separation layer 32 may bedisposed on top of the second lithium layer 22. Multi-layered structure28 can include four alternating layers of polymer (e.g., layers 43, 44,45, and 46) and single-ion conductive materials (e.g., layers 53, 54,55, and 56). Of course, greater than four polymer/single ion conductivelayers can be included. The structure can also include a currentcollector 81, and an outer layer 90 may be positioned between the anodelayer 20 and electrolyte 60 of the cell. In some cases, the layers thatprotect the anode, e.g., layers between and including separation layer30 and outer layer 90, can have a total overall thickness of, e.g., lessthan 5 mm, less than 3 mm, less than 2 mm, less than 1 mm, less than 700microns, less than 500 microns, less than 400 microns, less than 300microns, less than 250 microns, less than 200 microns, less than 150microns, less than 100 microns, less than 75 microns, or less than 50microns, less than 25 microns, or less than 10 microns.

Advantageously, batteries of the invention can be compact, light weightand can have high energy density. The layers of a cell between andincluding anode 20 and outer layer 90 may have a total thickness of lessthan 2 cm, less than 1.5 cm, less than 1 cm, less than 0.7 cm, less than0.5 cm, less than 0.3 cm, less than 1 mm, less than 700 microns, lessthan 500 microns, less than 400 microns, less than 300 microns, lessthan 250 microns, less than 200 microns, less than 150 microns, lessthan 100 microns, less than 75 microns, or less than 50 microns, lessthan 25 microns, or less than 10 microns, e.g., depending on theparticular application of the cell. Embodiments such as structures 14may be suitable for use with electrolytes such as aqueous solvents,e.g., water, and can operate as either primary or secondary cells.

Suitable cathode active materials for use in the cathode of theelectrochemical cells of the invention include, but are not limited to,electroactive transition metal chalcogenides, electroactive conductivepolymers, and electroactive sulfur-containing materials, andcombinations thereof. As used herein, the term “chalcogenides” pertainsto compounds that contain one or more of the elements of oxygen, sulfur,and selenium. Examples of suitable transition metal chalcogenidesinclude, but are not limited to, the electroactive oxides, sulfides, andselenides of transition metals selected from the group consisting of Mn,V, Cr, Ti, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re,Os, and Ir. In one embodiment, the transition metal chalcogenide isselected from the group consisting of the electroactive oxides ofnickel, manganese, cobalt, and vanadium, and the electroactive sulfidesof iron. In one embodiment, the cathode active layer comprises anelectroactive conductive polymer. Examples of suitable electroactiveconductive polymers include, but are not limited to, electroactive andelectronically conductive polymers selected from the group consisting ofpolypyrroles, polyanilines, polyphenylenes, polythiophenes, andpolyacetylenes. Preferred conductive polymers are polypyrroles,polyanilines, and polyacetylenes.

“Electroactive sulfur-containing materials,” as used herein, relates tocathode active materials which comprise the element sulfur in any form,wherein the electrochemical activity involves the breaking or forming ofsulfur-sulfur covalent bonds. Suitable electroactive sulfur-containingmaterials, include, but are not limited to, elemental sulfur and organicmaterials comprising sulfur atoms and carbon atoms, which may or may notbe polymeric. Suitable organic materials include those furthercomprising heteroatoms, conductive polymer segments, composites, andconductive polymers.

In some embodiments involving Li/S systems, the sulfur-containingmaterial, in its oxidized form, comprises a polysulfide moiety, S_(m),selected from the group consisting of covalent —S_(m)— moieties, ionic—S_(m) ⁻ moieties, and ionic S_(m) ²⁻ moieties, wherein m is an integerequal to or greater than 3. In one embodiment, m of the polysulfidemoiety, S_(m), of the sulfur-containing polymer is an integer equal toor greater than 6. In another embodiment, m of the polysulfide moiety,S_(m), of the sulfur-containing polymer is an integer equal to orgreater than 8. In another embodiment, the sulfur-containing material isa sulfur-containing polymer. In another embodiment, thesulfur-containing polymer has a polymer backbone chain and thepolysulfide moiety, S_(m), is covalently bonded by one or both of itsterminal sulfur atoms as a side group to the polymer backbone chain. Inyet another embodiment, the sulfur-containing polymer has a polymerbackbone chain and the polysulfide moiety, S_(m), is incorporated intothe polymer backbone chain by covalent bonding of the terminal sulfuratoms of the polysulfide moiety.

In one embodiment, the electroactive sulfur-containing materialcomprises greater than 50% by weight of sulfur. In another embodiment,the electroactive sulfur-containing material comprises greater than 75%by weight of sulfur. In yet another embodiment, the electroactivesulfur-containing material comprises greater than 90% by weight ofsulfur.

The nature of the electroactive sulfur-containing materials useful inthe practice of this invention may vary widely, as known in the art. Inone embodiment, the electroactive sulfur-containing material compriseselemental sulfur. In another embodiment, the electroactivesulfur-containing material comprises a mixture of elemental sulfur and asulfur-containing polymer.

Examples of sulfur-containing polymers include those described in: U.S.Pat. Nos. 5,601,947 and 5,690,702 to Skotheim et al.; U.S. Pat. Nos.5,529,860 and 6,117,590 to Skotheim et al.; and U.S. patent applicationSer. No. 08/995,122 now U.S. Pat. No. 6,201,100 issued Mar. 13, 2001, toGorkovenko et al. of the common assignee and PCT Publication No. WO99/33130. Other suitable electroactive sulfur-containing materialscomprising polysulfide linkages are described in U.S. Pat. No. 5,441,831to Skotheirn et al.; U.S. Pat. No. 4,664,991 to Perichaud et al., and inU.S. Pat. Nos. 5,723,230, 5,783,330, 5,792,575 and 5,882,819 to Naoi etal. Still further examples of electroactive sulfur-containing materialsinclude those comprising disulfide groups as described, for example in,U.S. Pat. No. 4,739,018 to Armand et al.; U.S. Pat. Nos. 4,833,048 and4,917,974, both to De Jonghe et al.; U.S. Pat. Nos. 5,162,175 and5,516,598, both to Visco et al.; and U.S. Pat. No. 5,324,599 to Oyama etal.

Cathodes may further comprise one or more conductive fillers to provideenhanced electronic conductivity. Examples of conductive fillersinclude, but are not limited to, those including conductive carbons,graphites, activated carbon fibers, non-activated carbon nanofibers,metal flakes, metal powders, metal fibers, carbon fabrics, metal mesh,and electrically conductive polymers. The amount of conductive filler,if present, may be present in the range of 2 to 30% by weight of thecathode active layer. The cathodes may also further comprise otheradditives including, but not limited to, metal oxides, aluminas,silicas, and transition metal chalcogenides.

Cathodes may also comprise a binder. The choice of binder material mayvary widely so long as it is inert with respect to the other materialsin the cathode. Useful binders are those materials, usually polymeric,that allow for ease of processing of battery electrode composites andare generally known to those skilled in the art of electrodefabrication. Examples of useful binders include polytetrafluoroethylenes(Teflon), polyvinylidene fluorides (PVF₂ or PVDF),ethylene-propylene-diene (EPDM) rubbers, polyethylene oxides (PEO), UVcurable acrylates, UV curable methacrylates, and heat curable divinylethers, and the like. The amount of binder, if present, may be presentin the range of 2 to 30% by weight of the cathode active layer.

The electrolytes used in electrochemical or battery cells can functionas a medium for the storage and transport of ions, and in the specialcase of solid electrolytes and gel electrolytes, these materials mayadditionally function as a separator between the anode and the cathode.As noted, in one set of embodiments an aqueous-based electrolyte isused. Any liquid, solid, or gel material capable of storing andtransporting ions may be used, so long as the material iselectrochemically and chemically unreactive with respect to the anodeand the cathode, and the material facilitates the transport of lithiumions between the anode and the cathode. The electrolyte may beelectronically non-conductive to prevent short circuiting between theanode and the cathode.

The electrolyte can comprise one or more ionic electrolyte salts toprovide ionic conductivity and one or more liquid electrolyte solvents,gel polymer materials, or polymer materials. Suitable non-aqueouselectrolytes may include organic electrolytes comprising one or morematerials selected from the group consisting of liquid electrolytes, gelpolymer electrolytes, and solid polymer electrolytes. Examples ofnon-aqueous electrolytes for lithium batteries are described by Dornineyin Lithium Batteries, New Materials, Developments and Perspectives,Chapter 4, pp. 137-165, Elsevier, Amsterdam (1994). Examples of gelpolymer electrolytes and solid polymer electrolytes are described byAlamgir et al. in Lithium Batteries, New Materials, Developments andPerspectives, Chapter 3, pp. 93-136, Elsevier, Amsterdam (1994).

Examples of useful non-aqueous liquid electrolyte solvents include, butare not limited to, non-aqueous organic solvents, such as, for example,N-methyl acetamide, acetonitrile, acetals, ketals, esters, carbonates,sulfones, sulfites, sulfolanes, aliphatic ethers, cyclic ethers, glymes,polyethers, phosphate esters, siloxanes, dioxolanes,N-alkylpyrrolidones, substituted forms of the foregoing, and blendsthereof. Fluorinated derivatives of the foregoing are also useful asliquid electrolyte solvents.

In some cases, aqueous solvents can be used as electrolytes for lithiumcells. Aqueous solvents can include water, which can contain othercomponents such as ionic salts. As noted above, in some embodiments, theelectrolyte can include species such as lithium hydroxide, or otherspecies rendering the electrolyte basic, so as to reduce theconcentration of hydrogen ions in the electrolyte.

Liquid electrolyte solvents can also be useful as plasticizers for gelpolymer electrolytes. Examples of useful gel polymer electrolytesinclude, but are not limited to, those comprising one or more polymersselected from the group consisting of polyethylene oxides, polypropyleneoxides, polyacrylonitriles, polysiloxanes, polyirnides,polyphosphazenes, polyethers, sulfonated polyimides, perfluorinatedmembranes (NAFION resins), polydivinyl polyethylene glycols,polyethylene glycol diacrylates, polyethylene glycol dimethacrylates,derivatives of the foregoing, copolymers of the foregoing, crosslinkedand network structures of the foregoing, and blends of the foregoing,and optionally, one or more plasticizers.

Examples of useful solid polymer electrolytes include, but are notlimited to, those comprising one or more polymers selected from thegroup consisting of polyethers, polyethylene oxides, polypropyleneoxides, polyimides, polyphosphazenes, polyacrylonitriles, polysiloxanes,derivatives of the foregoing, copolymers of the foregoing, crosslinkedand network structures of the foregoing, and blends of the foregoing.

In addition to electrolyte solvents, gelling agents, and polymers asknown in the art for forming electrolytes, the electrolyte may furthercomprise one or more ionic electrolyte salts, also as known in the art,to increase the ionic conductivity.

Examples of ionic electrolyte salts for use in the electrolytes of thepresent invention include, but are not limited to, LiSCN, LiBr, LiI,LiClO₄, LiAsF₆, LiSO₃CF₃, LiSO₃CH₃, LiBF₄, LiB(Ph)₄, LiPF₆,LiC(SO₂CF₃)₃, and LiN(SO₂CF₃)₂. Other electrolyte salts that may beuseful include lithium polysulfides (Li₂S_(x)), and lithium salts oforganic ionic polysulfides (LiS_(x)R)_(n), where x is an integer from 1to 20, n is an integer from 1 to 3, and R is an organic group, and thosedisclosed in U.S. Pat. No. 5,538,812 to Lee et al.

In some embodiments, electrochemical cells may further comprise aseparator interposed between the cathode and anode. The separator may bea solid non-conductive or insulative material which separates orinsulates the anode and the cathode from each other preventing shortcircuiting, and which permits the transport of ions between the anodeand the cathode.

The pores of the separator may be partially or substantially filled withelectrolyte. Separators may be supplied as porous free standing filmswhich are interleaved with the anodes and the cathodes during thefabrication of cells. Alternatively, the porous separator layer may beapplied directly to the surface of one of the electrodes, for example,as described in PCT Publication No. WO 99/33125 to Carlson et al. and inU.S. Pat. No. 5,194,341 to Bagley et al.

A variety of separator materials are known in the art. Examples ofsuitable solid porous separator materials include, but are not limitedto, polyolefins, such as, for example, polyethylenes and polypropylenes,glass fiber filter papers, and ceramic materials. Further examples ofseparators and separator materials suitable for use in this inventionare those comprising a microporous xerogel layer, for example, amicroporous pseudo-boehmite layer, which may be provided either as afree standing film or by a direct coating application on one of theelectrodes, as described in U.S. patent application Ser. Nos. 08/995,089and 09/215,112 by Carlson et al. of the common assignee. Solidelectrolytes and gel electrolytes may also function as a separator inaddition to their electrolyte function.

As noted above, a variety of ion-conductive species, and polymericspecies, are useful in connection with the invention. In some cases, ionconductive species that are also electrically conductive are employed.In other cases, ion conductor species that are substantiallynon-electrically conductive are employed.

Examples of ion conductor species, including single-ion-conductivespecies suitable for use in the invention, which are also substantiallyelectrically conductive, include lithium alloys such as lithium combinedwith Group 14 and Group 15 metals (e.g., Ge, Sn, Pb, As, Sb, Bi).Polymers that are conductive to single ions that are also substantiallyelectrically conductive include electrically conductive polymers (alsoknown as electronic polymers or conductive polymers) that are doped withlithium salts (e.g., LiSCN, LiBr, LiI, LiClO₄, LiAsF₆, LiSO₃CF₃,LiSO₃CH₃, LiBF₄, LiB(Ph)₄, LiPF₆, LiC(SO₂CF₃)₃, and LiN(SO₂CF₃)₂).Conductive polymers are known in the art; examples of such polymersinclude, but are not limited to, poly(acetylene)s, poly(pyrrole)s,poly(thiophene)s, poly(aniline)s, poly(fluorene)s, polynaphthalenes,poly(p-phenylene sulfide), and poly(para-phenylene vinylene)s.Electrically-conductive additives may also be added to polymers to formelectrically-conductive polymers. Certain electrically conductivematerials may have a conductivity of, e.g., greater than 10⁻² S/cm,greater than 10⁻¹ S/cm, greater than 1 S/cm, greater than 10¹ S/cm,greater than 10² S/cm, greater than 10³ S/cm, greater than 10⁴ S/cm, orgreater than 10⁵ S/cm. Examples of ion-conductive species that aresubstantially non-electrically conductive include non-electricallyconductive materials (e.g., electrically insulating materials) that aredoped with lithium salts. E.g., acrylate, polyethyleneoxide, silicones,polyvinylchlorides, and other insulating polymers that are doped withlithium salts can be ion-conductive but substantially non-electricallyconductive. In some embodiments, single-ion conductive materials canalso include non-polymeric materials. Certain non-electricallyconductive materials may have a resistivity of, e.g., greater than 10³ohm-cm, greater than 10⁴ ohm-cm, greater than 10⁵ ohm-cm, greater than10⁶ ohm-cm, greater than 10⁷ ohm-cm, or greater than 10⁸ ohm-cm. Thoseof ordinary skill in the art can select single ion conductive speciesthat are both substantially electrically conductive and substantiallynon-electrically conductive without undue experimentation, and canemploy a simple screening test to select from candidate materials. Thesimple screening test involves positioning a material as a separator inan electrochemical cell which, to function, requires passage of both anionic species and electrons across the material. This is a simple testto employ. If the material is substantially ionically conductive andelectronically conductive in this test, then resistance or resistivityacross the material will be low. Other simple tests can be conducted bythose of ordinary skill in the art.

The invention also employs polymeric materials, some of which areionically-conductive and some of which are electronically conductive. Asis the case for single ion conductive materials that are or are notelectronically conductive, those of ordinary skill in the art canreadily select, or formulate, such polymeric materials. These polymericmaterials also can be selected or formulated to have physical/mechanicalcharacteristics as described above by, for example, tailoring theamounts of components of polymer blends, adjusting the degree ofcross-linking (if any), etc. Simple screening tests such as thosedescribed above can be used to select polymers that have the appropriateionic and/or electronic properties.

Suitable polymer layers for use in a multi-layered structure includepolymers that are highly conductive towards lithium and minimallyconductive towards electrons include, for example, ionically conductivepolymers, sulfonated polymers, and hydrocarbon polymers. The selectionof the polymer will be dependent upon a number of factors including theproperties of electrolyte and cathode used in the cell. Suitableionically conductive polymers include, e.g., ionically conductivepolymers known to be useful in solid polymer electrolytes and gelpolymer electrolytes for lithium electrochemical cells, such as, forexample, polyethylene oxides. Suitable sulfonated polymers include,e.g., sulfonated siloxane polymers, sulfonatedpolystyrene-ethylene-butylene polymers, and sulfonated polystyrenepolymers. Suitable hydrocarbon polymers include, e.g.,ethylene-propylene polymers, polystyrene polymers, and the like.

Polymer layers of a multi-layered structure can also include crosslinkedpolymer materials formed from the polymerization of monomers such asalkyl acrylates, glycol acrylates, polyglycol acrylates, polyglycolvinyl ethers, polyglycol divinyl ethers, and those described in U.S.Pat. No. 6,183,901 to Ying et al. of the common assignee for protectivecoating layers for separator layers. For example, one such crosslinkedpolymer material is polydivinyl poly(ethylene glycol). The crosslinkedpolymer materials may further comprise salts, for example, lithiumsalts, to enhance ionic conductivity. In one embodiment, the polymerlayer of the multi-layered structure comprises a crosslinked polymer.

Other classes polymers that may be suitable for use in a polymer layerinclude, but are not limited to, polyamines (e.g., poly(ethylene imine)and polypropylene imine (PPI)); polyamides (e.g., polyamide (Nylon),poly(ε-caprolactam) (Nylon 6), poly(hexamethylene adipamide) (Nylon66)), polyimides (e.g., polyimide, polynitrile, andpoly(pyromellitimide-1,4-diphenyl ether) (Kapton)); vinyl polymers(e.g., polyacrylamide, poly(2-vinyl pyridine), poly(N-vinylpyrrolidone),poly(methylcyanoacrylate), poly(ethylcyanoacrylate),poly(butylcyanoacrylate), poly(isobutylcyanoacrylate), poly(vinylacetate), poly (vinyl alcohol), poly(vinyl chloride), poly(vinylfluoride), poly(2-vinyl pyridine), vinyl polymer, polychlorotrifluoroethylene, and poly(isohexylcynaoacrylate)); polyacetals; polyolefins(e.g., poly(butene-1), poly(n-pentene-2), polypropylene,polytetrafluoroethylene); polyesters (e.g., polycarbonate, polybutyleneterephthalate, polyhydroxybutyrate); polyethers (poly(ethylene oxide)(PEO), polypropylene oxide) (PPO), poly(tetramethylene oxide) (PTMO));vinylidene polymers (e.g., polyisobutylene, poly(methyl styrene),poly(methylmethacrylate) (PMMA), poly(vinylidene chloride), andpoly(vinylidene fluoride)); polyaramides (e.g., poly(imino-1,3-phenyleneiminoisophthaloyl) and poly(imino-1,4-phenylene iminoterephthaloyl));polyheteroaromatic compounds (e.g., polybenzimidazole (PBI),polybenzobisoxazole (PBO) and polybenzobisthiazole (PBT));polyheterocyclic compounds (e.g., polypyrrole); polyurethanes; phenolicpolymers (e.g., phenol-formaldehyde); polyalkynes (e.g., polyacetylene);polydienes (e.g., 1,2-polybutadiene, cis or trans-1,4-polybutadiene);polysiloxanes (e.g., poly(dimethylsiloxane) (PDMS),poly(diethylsiloxane) (PDES), polydiphenylsiloxane (PDPS), andpolymethylphenylsiloxane (PMPS)); and inorganic polymers (e.g.,polyphosphazene, polyphosphonate, polysilanes, polysilazanes). Themechanical and electronic properties (e.g., conductivity, resistivity)of these polymers are known. Accordingly, those of ordinary skill in theart can choose suitable polymers for use in lithium batteries, e.g.,based on their mechanical and/or electronic properties (e.g., ionicand/or electronic conductivity), and/or can modify such polymers to beionically conducting (e.g., conductive towards single ions) and/orelectronically conducting based on knowledge in the art, in combinationwith the description herein. For example, the polymer materials listedabove may further comprise salts, for example, lithium salts (e.g.,LiSCN, LiBr, LiI, LiClO₄, LiAsF₆, LiSO₃CF₃, LiSO₃CH₃, LiBF₄, LiB(Ph)₄,LiPF₆, LiC(SO₂CF₃)₃, and LiN(SO₂CF₃)₂), to enhance ionic conductivity.

The figures that accompany this disclosure are schematic only, andillustrate a substantially flat battery arrangement. It is to beunderstood that any electrochemical cell arrangement can be constructed,employing the principles of the present invention, in any configuration.For example, with reference to FIG. 1, anode 20 may be covered on theside opposite the side at which components 30, 40, and 50 areillustrated with a similar or identical set of components 30, 40, and50. In this arrangement, a substantially mirror-image structure iscreated with a mirror plane passing through anode 20. This would be thecase, for example, in a “rolled” battery configuration in which a layerof anode 20 is surrounded on each side by structures 30, 40, and 50 (or,in alternative arrangements layered structures illustrated in otherfigures herein). On the outside of each protective structure of theanode an electrolyte is provided and, opposite the electrolyte, acathode. In a rolled arrangement, or other arrangement includingmultiple layers of alternating anode and cathode functionality, thestructure involves anode, electrolyte, cathode, electrolyte, anode . . ., where each anode can include anode stabilization structures asdescribed in any part of this disclosure. Of course, at the outerboundaries of such an assembly, a “terminal” anode or cathode will bepresent. Circuitry to interconnect such a layered or rolled structure iswell-known in the art.

The following examples are intended to illustrate certain embodiments ofthe present invention, but are not to be construed as limiting and donot exemplify the full scope of the invention.

Example 1 Fabrication and Characterization of Lamanode Structures

Lamanode structures, e.g., structures including a first and secondlayers of Li separated by an embedded layer that is conductive to Liions, but substantially non-conductive to electrons, were fabricated bythermal evaporation (vacuum deposition) of Li on a PET substrate in twolayers of Li with different thickness. The two layers of Li wereseparated by an embedded layer of a low-conductive material, e.g.,LiPON, Li₃N or etc. The ratio of the thickness of top and bottom Lilayers was calculated based on a required DoD (depth of discharge) ofthe first discharge and was in the range between 0.2 to 0.4. A layer ofabout 0.01 to 1 micron LiPON was deposited on top of the bottom thickerLi layer by rf magnetron spattering from a Li₃PO₄ target in an N₂atmosphere. A thinner Li layer, e.g., 5 microns, was thermallyevaporated on top of the embedded layer.

The top (thinner) Li layer interfacing the electrolyte was dissolved atthe first discharge. During the next charge, Li was deposited on thesurface of the low-conductive LiPON embedded layer. During the seconddischarge, the Li deposit was dissolved to an extent depending on itscycling efficiency. The Li cycling efficiency(Eff) is defined byequation (1)

E _(eff) =Q _(a) /Q _(c)   (1),

where Q_(c) is the amount of Li deposit in Ah and Q_(a) is the amount ofdissolved Li in Ah. At a Li efficiency less than 1, an extra amount ofLi was dissolved from the bulk to complete a 100% cycle. E_(eff) for apractical system is typically higher than 0.98. Therefore, during thesecond discharge, a negligible amount of Li compared to the totalcathode charge was transferring from the bulk Li through the embeddedlayer(s) to the electrolyte and the cathode. This amount, 100 timessmaller than the amount of Li fluxing during the first anodicdissolution of Li and cathode lithiation, practically does not affectthe surface morphology of the bottom layer of Li and the adjustedprotective layer. The same scenario repeats with any subsequent 100%cycle to the cell end of life. As fewer defects, cracks and pinholes areformed on the Li and the adjusted embedded layer surfaces, the Licycling efficiency increases and the cycle life is longer. Such alaminode can be built in a cell along with a cathode, e.g., having 60 to75% sulfur and an electrolyte compatible with the sulfur chemistry.

In one embodiment, small prismatic cells including working and counterelectrodes with a geometric surface of 30 cm² and a polyethylene “Tonen”separator with a thickness of 16 microns between were sealed in analuminized plastic polyethylene bag of “Sealrite”. A solution of amixture of ethers and Li amide salt was added in the bag to serve as anelectrolyte. Two types of cells were built:

-   A) Li working electrode with a thickness about 25 microns made by    thermal evaporation of Li on 23 um PET called for simplicity. This    single-layered electrode was used as a control.-   B) Li working electrode with approximately the same thickness    including a three layered structure, e.g., a laminode. The laminode    was made by:-   i) 20 micron thermal evaporated Li on PET,-   ii) 0.075 micron of LiPON made by rf magnetron spattered from a    Li₃PO₄ target in an N₂ atmosphere on the top of the 20 micron Li;    and-   iii) 5 micron thermal evaporated Li on top of the layer of LiPON.

Both cell designs used a counter electrode of 25 micron thermalevaporated Li on 23 micron PET. The cells were discharged using the sameconditions of a current of 0.2 mA/cm² and a 20% DoD of Li. After thedischarge, the cells were opened in a glove box and the workingelectrode was studied by SEM.

The results from these experiments are shown in FIG. 8. FIG. 8A shows aSEM image of the control, and FIG. 8B shows the laminode structure. FIG.8C shows a 5000 times magnification of the structure shown in FIG. 8Bafter the removal of the top Li layer. It can be observed from the SEMpictures that the laminode structure is substantially free of anydefects such as cracks and pinholes. The single layered Li surfacecontrol, however, is strongly affected under the conditions of the firstdischarge.

This example shows that a laminode structure including a first andsecond layers of Li separated by an embedded layer that is conductive toLi ions, but substantially non-conductive to electrons, can increase thedesired properties of an electrochemical cell.

Example 2 Cycle Lives of Lamanode Structures

This example shows that the Li cycling efficiency increases and thecycle life is longer for cells including laminode structures compared tocells having single layers of base electrode materials.

To fabricate control cells, prismatic cells with thermal evaporated Lion one side of 23 micron thickness of PET, Separator Tonen and a cathodecontaining 65% S coated on one side of a Rexam Al foil were sealed in abag of Sealright. A mixture of ethers and Li imide salt was used as anelectrolyte. The working surface of the anode was 400 cm². The cellswere tasted for cycle life performance at a discharge current of 200 mAto a cut-off of 1.8 V, and charge current of 0.1 A for 4 hours. Cyclingresults obtained from three control cells were obtained.

The same cell design as described above was built but with a firstlaminode anode structure (or “sandwich anode”) instead of asingle-layered anode. The first laminode structure included a 20 micronthick thermal evaporated Li deposited on 23 microns of PET. A layer of0.02 micron of LiPON was rf magnetron sputtered from a Li₃PO₄ target inan N₂ atmosphere on top of the 20 micron thick Li, and 5 microns of Liwas thermally evaporated on top of the embedded LiPON layer. The sametest regime as for the control cells was applied for these cells.

The average FoM (Li cycling efficiency) of the controls was compared tothat of the first laminode-containing cells, with the result that asignificant improvement in the cycle life of the cells was realized.

Similar cells as those above were built and tested under the sameconditions using a second laminode structure, including a 20 micronthick thermally evaporated Li layer, a 0.075 micron thick LiPON layer,and a 5 micron thermally evaporated Li layer.

Comparing the FoM obtained from the second laminode structure with thatof the control, a significant improvement in the cycle life of thelaminode structures compared to the control anode was observed.

This example shows that the Li cycling efficiency increases and thecycle life is longer for cells including laminode structures compared tocells having single layers of base electrode materials.

Example 3 Effects of Different Types of Anode Protection on DischargeCapacity

This example shows effects of different types of anode protection ondischarge capacity of a cell.

The control used in these experiments included a VDLi/CO₂ structure,equivalent to a Li foil. A first test structure included aVDLi/CO₂/polymer (1500-2500 Angstroms) structure. A second teststructure included a VDLi/CO₂/polymer (1500-2500 Angstroms) structure. Athird test structure included a laminode (Sandwich anode) ofVDLi/LiPON/VDLi/CO₂/SPE. In this particular experiment, each of thecells were cycled several times, and an improvement of 30-40% in cyclelife was obtained when the cell included a polymer layer compared to acell without a polymer layer. A significant improvement in cycle lifewas obtained when a cell included an embedded layer of LiPON compared toa cell without an embedded layer. A cell that included a laminodestructure having an embedded layer and a polymer layer, e.g., aVDLi/LiPON/VDLi/CO2/SPE cell, had a significant improvement in cyclelife compared to a cell having single-layered anode, e.g., VDLi/CO₂. Inother embodiments, the degree of improvement in life-cycle can varydepending on, for example, the number of polymer layers, multi-layeredstructures, and embedded layers that make up the cell, and thethicknesses and materials used to form such structures.

This example shows that electrochemical cells including embedded andpolymer layers have increased cycle lives compared to cells without suchstructures.

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, kit, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,kits, and/or methods, if such features, systems, articles, materials,kits, and/or methods are not mutually inconsistent, is included withinthe scope of the present invention.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of” “only one of,” or“exactly one of.” “Consisting essentially of”, when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

It should also be understood that, unless clearly indicated to thecontrary, in any methods claimed herein that include more than one stepor act, the order of the steps or acts of the method is not necessarilylimited to the order in which the steps or acts of the method arerecited.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

1. An electrochemical cell comprising: an electrode comprising a baseelectrode material comprising an active electrode species that isdepleted and replated upon discharge and charge, respectively, of theelectrode, wherein the electrode comprises: a first layer comprising theactive electrode species; a second layer comprising the active electrodespecies; a single-ion conductive layer separating the first layer fromthe second layer and substantially preventing electronic communicationbetween the first and second layers across the layer; wherein the secondlayer is positioned so as to reside between the first layer and anelectrolyte used with the cell.
 2. An electrochemical cell as in claim1, wherein the single-ion conductive layer comprises at least oneelectronically conductive section.
 3. An electrochemical cell as inclaim 1, wherein the single-ion conductive layer comprises at least oneelectronically metal-containing layer.
 4. An electrochemical cell as inclaim 1, wherein the single-ion conductive layer comprises a metallayer.
 5. An electrochemical cell as in claim 1, further comprising aprotective layer positioned between the electrode and an electrolyteused with the cell, wherein the protective layer is a single-ionconductive, electronically conductive material.
 6. An electrochemicalcell as in claim 5, wherein the protective layer is substantiallysimilar in composition to the single-ion conductive layer separating thefirst layer from the second layer.
 7. An electrochemical cell as inclaim 1, further comprising a current collector in electroniccommunication with both the first layer and the second layer.
 8. Anelectrochemical cell as in claim 7, wherein the first and second layersdefine a layered structure with at least one edge, and the currentcollector is in contact with the edge of the anode across both the firstand second layers.
 9. A method of electrical energy storage and use,comprising: providing an electrochemical cell comprising an electrodecomprising a base electrode material comprising an active electrodespecies that is depleted and replated upon discharge and charge,respectively, of the electrode, wherein the electrode comprises: a firstlayer comprising the active electrode species; a second layer comprisingthe active electrode species; a single-ion conductive layer separatingthe first layer from the second layer and substantially preventingelectronic communication between the first and second layers across thesingle-ion conductive layer, wherein the second layer is positionedbetween the first layer and an electrolyte used with the cell;alternatively discharging current from the device to define an at leastpartially discharged device, and at least partially charging said atleast partially discharged device to define an at least partiallyrecharged device, whereupon the base electrode material from the firstlayer is consumed upon discharge to a greater extent than it is replatedupon charge, and base electrode material is replenished into the firstlayer, from the second layer, across the single-ion conductive,non-electronically conductive layer.
 10. A method as in claim 9, furthercomprising a counter electrode, wherein the second layer, prior to firstdischarge of the cell, comprises more active electrode species than isdepleted upon full discharge of the counter electrode.
 11. A method asin claim 10, the electrochemical cell further comprising a currentcollector in electronic communication with both the first layer and thesecond layer, the method comprising passing current through the firstlayer upon charge and discharge, and substantially inhibiting passage ofcharge through the second layer during charge and discharge.